extensions/notebook-renderers/src/color.ts/Color/getContrastRatio
class Color:	getContrastRatio(another: Color): number {
		const lum1 = this.getRelativeLuminance();
		const lum2 = another.getRelativeLuminance();
		return lum1 > lum2 ? (lum1 + 0.05) / (lum2 + 0.05) : (lum2 + 0.05) / (lum1 + 0.05);
	}