I'm sure I'm not alone in wishing that the Color struct had simple static Color.Random() and Color.RandomKnown() methods.
I use the following simple class to augment this missing function:
/// <summary>
/// Extra Functions for Colors
/// </summary>
public class ColorPlus
{

/// <summary>
/// returns a random Color
/// </summary>
public static Color Random
{
get
{
Random rand = new Random();
return Color.FromArgb(rand.Next(255), rand.Next(255), rand.Next(255));
}
}
}