/**
 * Color utility functions shared across the project.
 * Extracted from BrandColorsContext to allow reuse and isolated testing.
 */
/**
 * Converts a hex color string to its RGB components.
 * @param hex - Hex color string (with or without leading `#`)
 * @returns Object with `r`, `g`, `b` values (0–255), or `null` if invalid
 *
 * @example
 * hexToRgb('#3b82f6') // { r: 59, g: 130, b: 246 }
 * hexToRgb('3b82f6')  // { r: 59, g: 130, b: 246 }
 * hexToRgb('invalid') // null
 */
export declare function hexToRgb(hex: string): {
    r: number;
    g: number;
    b: number;
} | null;
/**
 * Converts RGB components to an `rgba()` CSS string.
 * @param r - Red (0–255)
 * @param g - Green (0–255)
 * @param b - Blue (0–255)
 * @param alpha - Alpha (0–1), defaults to 1
 *
 * @example
 * rgbToRgba(59, 130, 246, 0.5) // 'rgba(59, 130, 246, 0.5)'
 */
export declare function rgbToRgba(r: number, g: number, b: number, alpha?: number): string;
/**
 * Converts a hex color to an `rgba()` CSS string.
 * Returns `null` if the hex is invalid.
 *
 * @example
 * hexToRgba('#3b82f6', 0.15) // 'rgba(59, 130, 246, 0.15)'
 */
export declare function hexToRgba(hex: string, alpha?: number): string | null;
/**
 * Determines whether a hex color is considered "light" based on its luminance.
 * Uses the W3C relative luminance formula.
 *
 * @param hex - Hex color string
 * @returns `true` if the color is light, `false` if dark
 *
 * @example
 * isLightColor('#ffffff') // true
 * isLightColor('#000000') // false
 * isLightColor('#3b82f6') // false
 */
export declare function isLightColor(hex: string): boolean;