Bitmap bmp = new Bitmap(this.Width, this.Height);
this.DrawToBitmap(bmp, Rectangle.FromLTRB(0,0,this.Width, this.Height));
Color col = bmp.GetPixel(10, 10);
Console.WriteLine(col);
from http://www.80diy.com/home/20051127/05/4420725.html
SendKeys.SendWait("%{PRTSC}");
//Get the current form and store it to Bitmap.
Bitmap image = (Bitmap)Clipboard.GetDataObject().GetData(DataFormats.Bitmap);
//Get the color.
Color color = image.GetPixel(X, Y);