colorShade function
Shades a single Color and returns the new shaded value.
Implementation
Color colorShade(Color color, int i) => Color.rgb(
(color.red * (1 - 0.1 * i)).round(),
(color.green * (1 - 0.1 * i)).round(),
(color.blue * (1 - 0.1 * i)).round(),
);