analogous method
Returns count analogous colors spaced angle degrees apart on the
color wheel, centered on this color.
Colors.blue.analogous() // 3 colors around blue
Implementation
List<Color> analogous({int count = 3, double angle = 30}) {
final hsl = HSLColor.fromColor(this);
final half = (count ~/ 2);
return List.generate(
count,
(i) => hsl.withHue((hsl.hue + angle * (i - half)) % 360).toColor(),
);
}