/**
 * Lightweight color manipulation helpers.
 * Extracted from statisticalOverlays to avoid pulling the heavy module
 * into the main barrel import graph.
 */
/**
 * Darken a CSS hex color by a factor (0–1). factor=0.5 darkens by 50%.
 * Returns the original string unchanged if it's not a valid hex color.
 */
export declare function darkenColor(hex: string, factor?: number): string;
/**
 * Lighten a CSS hex color by a factor (0–1). factor=0.5 lightens by 50%.
 * Returns the original string unchanged if it's not a valid hex color.
 */
export declare function lightenColor(hex: string, factor?: number): string;
