/** Returns true when the given hex color looks dark (relative luminance < 0.5). */
export declare function isDarkColor(color: string): boolean;
/**
 * Move a hex color toward the opposite end of the scale by `amount` (0-1).
 *
 * Dimming is only feedback when there is brightness to remove. A near-black fill has none, so
 * `filter: brightness()` leaves it looking inert — the case a template hits whenever it carries
 * its own dark color into dark mode. Lightening a dark color and darkening a light one gives a
 * step that is visible whichever end the fill sits at. Returns undefined for anything that is
 * not hex, leaving the caller on its own fallback.
 */
export declare function shadeTowardMiddle(color: string, amount: number): string | undefined;
export declare const CourierColors: {
    black: {
        400: string;
        500: string;
        50010: string;
        50020: string;
    };
    gray: {
        200: string;
        400: string;
        500: string;
        600: string;
        650: string;
        700: string;
        800: string;
    };
    white: {
        500: string;
        50010: string;
        50020: string;
    };
    blue: {
        300: string;
        400: string;
        500: string;
        600: string;
    };
};
/**
 * Default primary color used across Courier UI components (checkboxes, radios, etc.).
 * Matches the inbox primary color for consistency.
 * @public
 */
export declare const COURIER_DEFAULT_PRIMARY_COLOR: string;