RgbColor constructor
Creates a Color using a vector describing its red, green, and blue values.
The value for r, g, and b should be in the range between 0 and 255 (inclusive). Values above this range will be assumed to be a value of 255, and values below this range will be assumed to be a value of 0.
Implementation
const RgbColor(this.r, this.g, this.b);