diff --git a/apps/web/src/App.tsx b/apps/web/src/App.tsx
index cb4927c..fe73588 100644
--- a/apps/web/src/App.tsx
+++ b/apps/web/src/App.tsx
@@ -30,6 +30,7 @@ import { useBulkImport } from "./hooks/use-bulk-import";
 import { useEncounter } from "./hooks/use-encounter";
 import { usePlayerCharacters } from "./hooks/use-player-characters";
 import { useSidePanelState } from "./hooks/use-side-panel-state";
+import { useTheme } from "./hooks/use-theme";
 import { cn } from "./lib/utils";
 
 function rollDice(): number {
@@ -115,6 +116,7 @@ export function App() {
 
 	const bulkImport = useBulkImport();
 	const sidePanel = useSidePanelState();
+	const { preference: themePreference, cycleTheme } = useTheme();
 
 	const [rollSkippedCount, setRollSkippedCount] = useState(0);
 	const [rollSingleSkipped, setRollSingleSkipped] = useState(false);
@@ -263,6 +265,8 @@ export function App() {
 								showRollAllInitiative={hasCreatureCombatants}
 								rollAllInitiativeDisabled={!canRollAllInitiative}
 								onOpenSourceManager={sidePanel.showSourceManager}
+								themePreference={themePreference}
+								onCycleTheme={cycleTheme}
 								autoFocus
 							/>
 						</div>
@@ -325,6 +329,8 @@ export function App() {
 								showRollAllInitiative={hasCreatureCombatants}
 								rollAllInitiativeDisabled={!canRollAllInitiative}
 								onOpenSourceManager={sidePanel.showSourceManager}
+								themePreference={themePreference}
+								onCycleTheme={cycleTheme}
 							/>
 						</div>
 					</>
diff --git a/apps/web/src/components/__tests__/combatant-row.test.tsx b/apps/web/src/components/__tests__/combatant-row.test.tsx
index b169bce..9850f49 100644
--- a/apps/web/src/components/__tests__/combatant-row.test.tsx
+++ b/apps/web/src/components/__tests__/combatant-row.test.tsx
@@ -75,7 +75,7 @@ describe("CombatantRow", () => {
 	it("active combatant gets active border styling", () => {
 		const { container } = renderRow({ isActive: true });
 		const row = container.firstElementChild;
-		expect(row?.className).toContain("border-accent/40");
+		expect(row?.className).toContain("border-active-row-border");
 	});
 
 	it("unconscious combatant (currentHp === 0) gets dimmed styling", () => {
diff --git a/apps/web/src/components/action-bar.tsx b/apps/web/src/components/action-bar.tsx
index 16199c1..8f284f4 100644
--- a/apps/web/src/components/action-bar.tsx
+++ b/apps/web/src/components/action-bar.tsx
@@ -6,7 +6,10 @@ import {
 	Import,
 	Library,
 	Minus,
+	Monitor,
+	Moon,
 	Plus,
+	Sun,
 	Users,
 } from "lucide-react";
 import React, { type RefObject, useDeferredValue, useState } from "react";
@@ -43,6 +46,8 @@ interface ActionBarProps {
 	rollAllInitiativeDisabled?: boolean;
 	onOpenSourceManager?: () => void;
 	autoFocus?: boolean;
+	themePreference?: "system" | "light" | "dark";
+	onCycleTheme?: () => void;
 }
 
 function creatureKey(r: SearchResult): string {
@@ -171,7 +176,7 @@ function AddModeSuggestions({
 													>
 														<Minus className="h-3 w-3" />
 													</button>
-													<span className="min-w-5 rounded-full bg-accent px-1.5 py-0.5 text-center font-medium text-foreground">
+													<span className="min-w-5 rounded-full bg-accent px-1.5 py-0.5 text-center font-medium text-primary-foreground">
 														{queued.count}
 													</span>
 													<button
@@ -215,12 +220,26 @@ function AddModeSuggestions({
 	);
 }
 
+const THEME_ICONS = {
+	system: Monitor,
+	light: Sun,
+	dark: Moon,
+} as const;
+
+const THEME_LABELS = {
+	system: "Theme: System",
+	light: "Theme: Light",
+	dark: "Theme: Dark",
+} as const;
+
 function buildOverflowItems(opts: {
 	onManagePlayers?: () => void;
 	onOpenSourceManager?: () => void;
 	bestiaryLoaded: boolean;
 	onBulkImport?: () => void;
 	bulkImportDisabled?: boolean;
+	themePreference?: "system" | "light" | "dark";
+	onCycleTheme?: () => void;
 }): OverflowMenuItem[] {
 	const items: OverflowMenuItem[] = [];
 	if (opts.onManagePlayers) {
@@ -245,6 +264,16 @@ function buildOverflowItems(opts: {
 			disabled: opts.bulkImportDisabled,
 		});
 	}
+	if (opts.onCycleTheme) {
+		const pref = opts.themePreference ?? "system";
+		const ThemeIcon = THEME_ICONS[pref];
+		items.push({
+			icon: <ThemeIcon className="h-4 w-4" />,
+			label: THEME_LABELS[pref],
+			onClick: opts.onCycleTheme,
+			keepOpen: true,
+		});
+	}
 	return items;
 }
 
@@ -265,6 +294,8 @@ export function ActionBar({
 	rollAllInitiativeDisabled,
 	onOpenSourceManager,
 	autoFocus,
+	themePreference,
+	onCycleTheme,
 }: Readonly<ActionBarProps>) {
 	const [nameInput, setNameInput] = useState("");
 	const [suggestions, setSuggestions] = useState<SearchResult[]>([]);
@@ -454,6 +485,8 @@ export function ActionBar({
 		bestiaryLoaded,
 		onBulkImport,
 		bulkImportDisabled,
+		themePreference,
+		onCycleTheme,
 	});
 
 	return (
diff --git a/apps/web/src/components/combatant-row.tsx b/apps/web/src/components/combatant-row.tsx
index 7ea7ef6..a5cd6e0 100644
--- a/apps/web/src/components/combatant-row.tsx
+++ b/apps/web/src/components/combatant-row.tsx
@@ -367,9 +367,9 @@ function rowBorderClass(
 	isConcentrating: boolean | undefined,
 ): string {
 	if (isActive && isConcentrating)
-		return "border border-l-2 border-accent/40 border-l-purple-400 bg-accent/10 card-glow";
+		return "border border-l-2 border-active-row-border border-l-purple-400 bg-active-row-bg card-glow";
 	if (isActive)
-		return "border border-l-2 border-accent/40 bg-accent/10 card-glow";
+		return "border border-l-2 border-active-row-border bg-active-row-bg card-glow";
 	if (isConcentrating)
 		return "border border-l-2 border-transparent border-l-purple-400";
 	return "border border-l-2 border-transparent";
diff --git a/apps/web/src/components/hp-adjust-popover.tsx b/apps/web/src/components/hp-adjust-popover.tsx
index 3ac3cbc..7f73d49 100644
--- a/apps/web/src/components/hp-adjust-popover.tsx
+++ b/apps/web/src/components/hp-adjust-popover.tsx
@@ -113,7 +113,7 @@ export function HpAdjustPopover({ onAdjust, onClose }: HpAdjustPopoverProps) {
 				<button
 					type="button"
 					disabled={!isValid}
-					className="inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-md text-red-400 transition-colors hover:bg-red-950 hover:text-red-300 disabled:pointer-events-none disabled:opacity-50"
+					className="inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-md text-red-400 transition-colors hover:bg-hp-damage-hover-bg hover:text-red-300 disabled:pointer-events-none disabled:opacity-50"
 					onClick={() => applyDelta(-1)}
 					title="Apply damage"
 					aria-label="Apply damage"
@@ -123,7 +123,7 @@ export function HpAdjustPopover({ onAdjust, onClose }: HpAdjustPopoverProps) {
 				<button
 					type="button"
 					disabled={!isValid}
-					className="inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-md text-emerald-400 transition-colors hover:bg-emerald-950 hover:text-emerald-300 disabled:pointer-events-none disabled:opacity-50"
+					className="inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-md text-emerald-400 transition-colors hover:bg-hp-heal-hover-bg hover:text-emerald-300 disabled:pointer-events-none disabled:opacity-50"
 					onClick={() => applyDelta(1)}
 					title="Apply healing"
 					aria-label="Apply healing"
diff --git a/apps/web/src/components/stat-block.tsx b/apps/web/src/components/stat-block.tsx
index 5c98efa..702a3be 100644
--- a/apps/web/src/components/stat-block.tsx
+++ b/apps/web/src/components/stat-block.tsx
@@ -30,7 +30,7 @@ function PropertyLine({
 
 function SectionDivider() {
 	return (
-		<div className="my-2 h-px bg-gradient-to-r from-amber-800/60 via-amber-700/40 to-transparent" />
+		<div className="my-2 h-px bg-gradient-to-r from-stat-divider-from via-stat-divider-via to-transparent" />
 	);
 }
 
@@ -54,7 +54,7 @@ export function StatBlock({ creature }: Readonly<StatBlockProps>) {
 		<div className="space-y-1 text-foreground">
 			{/* Header */}
 			<div>
-				<h2 className="font-bold text-amber-400 text-xl">{creature.name}</h2>
+				<h2 className="font-bold text-stat-heading text-xl">{creature.name}</h2>
 				<p className="text-muted-foreground text-sm italic">
 					{creature.size} {creature.type}, {creature.alignment}
 				</p>
@@ -194,7 +194,7 @@ export function StatBlock({ creature }: Readonly<StatBlockProps>) {
 			{creature.actions && creature.actions.length > 0 && (
 				<>
 					<SectionDivider />
-					<h3 className="font-bold text-amber-400 text-base">Actions</h3>
+					<h3 className="font-bold text-base text-stat-heading">Actions</h3>
 					<div className="space-y-2">
 						{creature.actions.map((a) => (
 							<div key={a.name} className="text-sm">
@@ -209,7 +209,9 @@ export function StatBlock({ creature }: Readonly<StatBlockProps>) {
 			{creature.bonusActions && creature.bonusActions.length > 0 && (
 				<>
 					<SectionDivider />
-					<h3 className="font-bold text-amber-400 text-base">Bonus Actions</h3>
+					<h3 className="font-bold text-base text-stat-heading">
+						Bonus Actions
+					</h3>
 					<div className="space-y-2">
 						{creature.bonusActions.map((a) => (
 							<div key={a.name} className="text-sm">
@@ -224,7 +226,7 @@ export function StatBlock({ creature }: Readonly<StatBlockProps>) {
 			{creature.reactions && creature.reactions.length > 0 && (
 				<>
 					<SectionDivider />
-					<h3 className="font-bold text-amber-400 text-base">Reactions</h3>
+					<h3 className="font-bold text-base text-stat-heading">Reactions</h3>
 					<div className="space-y-2">
 						{creature.reactions.map((a) => (
 							<div key={a.name} className="text-sm">
@@ -239,7 +241,7 @@ export function StatBlock({ creature }: Readonly<StatBlockProps>) {
 			{!!creature.legendaryActions && (
 				<>
 					<SectionDivider />
-					<h3 className="font-bold text-amber-400 text-base">
+					<h3 className="font-bold text-base text-stat-heading">
 						Legendary Actions
 					</h3>
 					<p className="text-muted-foreground text-sm italic">
diff --git a/apps/web/src/components/ui/overflow-menu.tsx b/apps/web/src/components/ui/overflow-menu.tsx
index 19199db..f8f1fd7 100644
--- a/apps/web/src/components/ui/overflow-menu.tsx
+++ b/apps/web/src/components/ui/overflow-menu.tsx
@@ -7,6 +7,7 @@ export interface OverflowMenuItem {
 	readonly label: string;
 	readonly onClick: () => void;
 	readonly disabled?: boolean;
+	readonly keepOpen?: boolean;
 }
 
 interface OverflowMenuProps {
@@ -58,7 +59,7 @@ export function OverflowMenu({ items }: OverflowMenuProps) {
 							disabled={item.disabled}
 							onClick={() => {
 								item.onClick();
-								setOpen(false);
+								if (!item.keepOpen) setOpen(false);
 							}}
 						>
 							{item.icon}
diff --git a/apps/web/src/hooks/use-theme.ts b/apps/web/src/hooks/use-theme.ts
new file mode 100644
index 0000000..ce99866
--- /dev/null
+++ b/apps/web/src/hooks/use-theme.ts
@@ -0,0 +1,98 @@
+import { useCallback, useEffect, useSyncExternalStore } from "react";
+
+type ThemePreference = "system" | "light" | "dark";
+type ResolvedTheme = "light" | "dark";
+
+const STORAGE_KEY = "initiative:theme";
+
+const listeners = new Set<() => void>();
+let currentPreference: ThemePreference = loadPreference();
+
+function loadPreference(): ThemePreference {
+	try {
+		const raw = localStorage.getItem(STORAGE_KEY);
+		if (raw === "light" || raw === "dark" || raw === "system") return raw;
+	} catch {
+		// storage unavailable
+	}
+	return "system";
+}
+
+function savePreference(pref: ThemePreference): void {
+	try {
+		localStorage.setItem(STORAGE_KEY, pref);
+	} catch {
+		// quota exceeded or storage unavailable
+	}
+}
+
+function getSystemTheme(): ResolvedTheme {
+	if (typeof globalThis.matchMedia !== "function") return "dark";
+	return globalThis.matchMedia("(prefers-color-scheme: light)").matches
+		? "light"
+		: "dark";
+}
+
+function resolve(pref: ThemePreference): ResolvedTheme {
+	return pref === "system" ? getSystemTheme() : pref;
+}
+
+function applyTheme(resolved: ResolvedTheme): void {
+	document.documentElement.dataset.theme = resolved;
+}
+
+function notifyAll(): void {
+	for (const listener of listeners) {
+		listener();
+	}
+}
+
+// Apply on load
+applyTheme(resolve(currentPreference));
+
+// Listen for OS preference changes
+if (typeof globalThis.matchMedia === "function") {
+	globalThis
+		.matchMedia("(prefers-color-scheme: light)")
+		.addEventListener("change", () => {
+			if (currentPreference === "system") {
+				applyTheme(resolve("system"));
+				notifyAll();
+			}
+		});
+}
+
+function subscribe(callback: () => void): () => void {
+	listeners.add(callback);
+	return () => listeners.delete(callback);
+}
+
+function getSnapshot(): ThemePreference {
+	return currentPreference;
+}
+
+const CYCLE: ThemePreference[] = ["system", "light", "dark"];
+
+export function useTheme() {
+	const preference = useSyncExternalStore(subscribe, getSnapshot);
+	const resolved = resolve(preference);
+
+	useEffect(() => {
+		applyTheme(resolved);
+	}, [resolved]);
+
+	const setPreference = useCallback((pref: ThemePreference) => {
+		currentPreference = pref;
+		savePreference(pref);
+		applyTheme(resolve(pref));
+		notifyAll();
+	}, []);
+
+	const cycleTheme = useCallback(() => {
+		const idx = CYCLE.indexOf(currentPreference);
+		const next = CYCLE[(idx + 1) % CYCLE.length];
+		setPreference(next);
+	}, [setPreference]);
+
+	return { preference, resolved, setPreference, cycleTheme } as const;
+}
diff --git a/apps/web/src/index.css b/apps/web/src/index.css
index c2df818..0aef3aa 100644
--- a/apps/web/src/index.css
+++ b/apps/web/src/index.css
@@ -19,12 +19,47 @@
 	--color-hover-neutral-bg: oklch(0.623 0.214 259 / 0.15);
 	--color-hover-action-bg: var(--color-muted);
 	--color-hover-destructive-bg: transparent;
+	--color-stat-heading: #fbbf24;
+	--color-stat-divider-from: oklch(0.5 0.1 65 / 0.6);
+	--color-stat-divider-via: oklch(0.5 0.1 65 / 0.4);
+	--color-hp-damage-hover-bg: oklch(0.25 0.05 25);
+	--color-hp-heal-hover-bg: oklch(0.25 0.05 155);
+	--color-active-row-bg: oklch(0.623 0.214 259 / 0.1);
+	--color-active-row-border: oklch(0.623 0.214 259 / 0.4);
 	--radius-sm: 0.25rem;
 	--radius-md: 0.5rem;
 	--radius-lg: 0.75rem;
 	--font-sans: "Inter", ui-sans-serif, system-ui, sans-serif;
 }
 
+[data-theme="light"] {
+	--color-background: #eeecea;
+	--color-foreground: #374151;
+	--color-muted: #e0ddd9;
+	--color-muted-foreground: #6b7280;
+	--color-card: #f7f6f4;
+	--color-card-foreground: #374151;
+	--color-border: #ddd9d5;
+	--color-input: #cdc8c3;
+	--color-primary: #2563eb;
+	--color-primary-foreground: #ffffff;
+	--color-accent: #2563eb;
+	--color-destructive: #dc2626;
+	--color-hover-neutral: var(--color-primary);
+	--color-hover-action: var(--color-primary);
+	--color-hover-destructive: var(--color-destructive);
+	--color-hover-neutral-bg: oklch(0.623 0.214 259 / 0.08);
+	--color-hover-action-bg: var(--color-muted);
+	--color-hover-destructive-bg: transparent;
+	--color-stat-heading: #92400e;
+	--color-stat-divider-from: oklch(0.55 0.1 65 / 0.5);
+	--color-stat-divider-via: oklch(0.55 0.1 65 / 0.25);
+	--color-hp-damage-hover-bg: #fef2f2;
+	--color-hp-heal-hover-bg: #ecfdf5;
+	--color-active-row-bg: oklch(0.623 0.214 259 / 0.08);
+	--color-active-row-border: oklch(0.623 0.214 259 / 0.25);
+}
+
 @keyframes concentration-shake {
 	0% {
 		translate: 0;
@@ -178,6 +213,11 @@
 	box-shadow:
 		0 0 15px -2px oklch(0.623 0.214 259 / 0.2),
 		inset 0 1px 0 0 oklch(0.7 0.15 259 / 0.1);
+
+	[data-theme="light"] & {
+		background-image: none;
+		box-shadow: 0 1px 3px 0 oklch(0 0 0 / 0.08);
+	}
 }
 
 @utility panel-glow {
@@ -189,6 +229,11 @@
 	box-shadow:
 		0 0 20px -2px oklch(0.623 0.214 259 / 0.15),
 		inset 0 1px 0 0 oklch(0.7 0.15 259 / 0.1);
+
+	[data-theme="light"] & {
+		background-image: none;
+		box-shadow: -1px 0 6px 0 oklch(0 0 0 / 0.1);
+	}
 }
 
 * {
@@ -207,3 +252,7 @@ body {
 	color: var(--color-foreground);
 	font-family: var(--font-sans);
 }
+
+[data-theme="light"] body {
+	background-image: none;
+}