darken method
Implementation
ColorValue darken(double amount) {
final rgb = toHSL().darken(amount).toRGB();
return ColorValue._(rgb[0], rgb[1], rgb[2], a);
}
ColorValue darken(double amount) {
final rgb = toHSL().darken(amount).toRGB();
return ColorValue._(rgb[0], rgb[1], rgb[2], a);
}