private Bitmap bufor = null;
private void Form1_Paint(object sender, PaintEventArgs e){
    Graphics g = e.Graphics;
    bufor = new Bitmap(this.ClientSize.Width, this.ClientSize.Height);

    for(int x=0;x< this.ClientSize.Width;x++){
        for(int y=0;y<this.ClientSize.Height;y++){
            int G = (int)(255 * 0.5*(1+Math.Sin((y-x)/10.0)));
            int R = (int)(255 * 0.5*(1+Math.Sin((x+y)/10.0)));
            bufor.SetPixel(x,y,Color.FromArgb(R,G,0));
        }
    }
    g.DrawImage(bufor,0,0);

}