import type { NamedCSSColour, WCAG } from "./types";
/**
 * Calculates the contrast ratio between two named CSS colours in.
 *
 * See list here https://developer.mozilla.org/en-US/docs/Web/CSS/named-color
 * @param colour1 The first named CSS colour
 * @param colour2 The second named CSS colour
 * @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 getContrastRatioFromNamedCSSColour(colour1: NamedCSSColour, colour2: NamedCSSColour, standard: WCAG): number | null;