withRed method
Returns a new color that matches this color with the red channel replaced
with r
(which ranges from 0 to 255).
Out of range values will have unexpected effects.
Implementation
Color withRed(int r) {
return Color.fromARGB((a * 255.0).round() & 0xff, r,
(g * 255.0).round() & 0xff, (b * 255.0).round() & 0xff);
}