This post shows you how to random color in C#.
You can use Random class
Random rnd = new Random();
then use the Next method to random value.
Color color = Color.FromArgb(rnd.Next(256), rnd.Next(256), rnd.Next(256));
Using FormArgb method to create color from random value.
As you know, maximum value is 256 colors. We will random value from 0 to 256