diff --git a/packages/appearance/src/color-vision.ts b/packages/appearance/src/color-vision.ts
new file mode 100644
index 0000000..bed37a8
--- /dev/null
+++ b/packages/appearance/src/color-vision.ts
@@ -0,0 +1,103 @@
+import type { ThemeScheme } from "./themes"
+
+/**
+ * Color-vision assistance modes.
+ *
+ * These modes select palettes that are easier to distinguish. They are not
+ * simulations of how another person sees the interface and intentionally do
+ * not apply a filter to images or the complete document.
+ */
+export type ColorVisionMode = "standard" | "protan" | "deutan" | "tritan"
+
+export const colorVisionModes = [
+  "standard",
+  "protan",
+  "deutan",
+  "tritan",
+] as const satisfies readonly ColorVisionMode[]
+
+export const COLOR_VISION_ATTRIBUTE = "data-ui-color-vision"
+
+type ColorVisionVariables = Readonly<
+  Record<
+    "destructive" | "chart-1" | "chart-2" | "chart-3" | "chart-4" | "chart-5",
+    string
+  >
+>
+
+/**
+ * Palettes for semantic data colors that commonly need to be distinguished.
+ * Components must still pair color with text, icons, shapes, or patterns.
+ */
+export const colorVisionPalettes: Readonly<
+  Record<
+    Exclude<ColorVisionMode, "standard">,
+    Record<ThemeScheme, ColorVisionVariables>
+  >
+> = {
+  protan: {
+    light: {
+      destructive: "#b54a00",
+      "chart-1": "#0072b2",
+      "chart-2": "#e69f00",
+      "chart-3": "#009e73",
+      "chart-4": "#cc79a7",
+      "chart-5": "#6b5ca5",
+    },
+    dark: {
+      destructive: "#ff9d66",
+      "chart-1": "#56b4e9",
+      "chart-2": "#f0e442",
+      "chart-3": "#65d5b3",
+      "chart-4": "#e8a4ce",
+      "chart-5": "#afa4e8",
+    },
+  },
+  deutan: {
+    light: {
+      destructive: "#a64b00",
+      "chart-1": "#005f9e",
+      "chart-2": "#d88c00",
+      "chart-3": "#8a6f00",
+      "chart-4": "#bd63a0",
+      "chart-5": "#168c9e",
+    },
+    dark: {
+      destructive: "#ff9d66",
+      "chart-1": "#65bff0",
+      "chart-2": "#f3c969",
+      "chart-3": "#d7c85d",
+      "chart-4": "#e5a0cf",
+      "chart-5": "#63c7d5",
+    },
+  },
+  tritan: {
+    light: {
+      destructive: "#b83261",
+      "chart-1": "#b83280",
+      "chart-2": "#008f72",
+      "chart-3": "#d55e00",
+      "chart-4": "#6b5ca5",
+      "chart-5": "#53606d",
+    },
+    dark: {
+      destructive: "#f27ca5",
+      "chart-1": "#ed8bc9",
+      "chart-2": "#62d1b3",
+      "chart-3": "#ff9d66",
+      "chart-4": "#afa4e8",
+      "chart-5": "#b8c2cc",
+    },
+  },
+}
+
+export function isColorVisionMode(value: unknown): value is ColorVisionMode {
+  return colorVisionModes.some((mode) => mode === value)
+}
+
+export function getColorVisionCssVariables(
+  mode: ColorVisionMode,
+  scheme: ThemeScheme
+): ColorVisionVariables | undefined {
+  return mode === "standard" ? undefined : colorVisionPalettes[mode][scheme]
+}
diff --git a/packages/appearance/src/display.ts b/packages/appearance/src/display.ts
new file mode 100644
index 0000000..af59c0d
--- /dev/null
+++ b/packages/appearance/src/display.ts
@@ -0,0 +1,77 @@
+import type { ThemeScheme } from "./themes"
+
+export type Brightness = "dim" | "normal" | "bright"
+export type MotionMode = "system" | "reduce" | "full"
+export type ResolvedMotionMode = Exclude<MotionMode, "system">
+export type TextScale = "100" | "125" | "150" | "200"
+
+export const brightnessModes = [
+  "dim",
+  "normal",
+  "bright",
+] as const satisfies readonly Brightness[]
+export const motionModes = [
+  "system",
+  "reduce",
+  "full",
+] as const satisfies readonly MotionMode[]
+export const textScales = [
+  "100",
+  "125",
+  "150",
+  "200",
+] as const satisfies readonly TextScale[]
+
+export const BRIGHTNESS_ATTRIBUTE = "data-ui-brightness"
+export const MOTION_ATTRIBUTE = "data-ui-motion"
+export const TEXT_SCALE_ATTRIBUTE = "data-ui-text-scale"
+
+const surfaceVariableNames = [
+  "background",
+  "card",
+  "popover",
+  "secondary",
+  "muted",
+  "highlight",
+  "sidebar",
+] as const
+
+export function isBrightness(value: unknown): value is Brightness {
+  return brightnessModes.some((mode) => mode === value)
+}
+
+export function isMotionMode(value: unknown): value is MotionMode {
+  return motionModes.some((mode) => mode === value)
+}
+
+export function isTextScale(value: unknown): value is TextScale {
+  return textScales.some((scale) => scale === value)
+}
+
+/**
+ * Adjusts interface surfaces without filtering media, illustrations, or brand
+ * colors. Foreground colors are preserved so dimming does not reduce contrast.
+ */
+export function applyBrightnessToTheme(
+  variables: Record<string, string>,
+  brightness: Brightness,
+  scheme: ThemeScheme
+): Record<string, string> {
+  if (brightness === "normal") return variables
+
+  const target = brightness === "dim" ? "black" : "white"
+  const amount = {
+    bright: scheme === "light" ? 12 : 8,
+    dim: scheme === "light" ? 5 : 12,
+  }[brightness]
+  const adjusted = { ...variables }
+
+  for (const name of surfaceVariableNames) {
+    const value = variables[name]
+    if (value) {
+      adjusted[name] = `color-mix(in oklch,${value},${target} ${amount}%)`
+    }
+  }
+
+  return adjusted
+}