import type { WCAG } from "./types";
/**
 * Calculates the contrast ratio between two colours in hexadecimal format.
 * @param colour1 The first colour in hexadecimal format
 * @param colour2 The second colour in hexadecimal format
 * @param standard The standard to evaluate the contrast ratio against, defaults to WCAG2.1
 * @returns The contrast ratio between the two colours truncated to 3 decimal places
 */
export declare function getContrastRatioFromHex(colour1: string, colour2: string, standard: WCAG): number | null;