生成随机色（深色）

  public static Color GetRandomColor()
        {
            //Random RandomNum_First = new Random((int)DateTime.Now.Ticks);
            //System.Threading.Thread.Sleep(100);
            //Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);

            ////  为了在白色背景上显示，尽量生成深色 
            //int int_Red = RandomNum_First.Next(256);
            //int int_Green = RandomNum_Sencond.Next(256);
            //int int_Blue = (int_Red + int_Green > 400) ? 0 : 400 - int_Red - int_Green;
            //int_Blue = (int_Blue > 255) ? 255 : int_Blue;

            //return Color.FromArgb(int_Red, int_Green, int_Blue);

            Random RandomNum_First = new Random((int)DateTime.Now.Ticks);
            System.Threading.Thread.Sleep(50);
            Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);
            System.Threading.Thread.Sleep(100);
            Random RandomNum_Third = new Random((int)DateTime.Now.Ticks);

            int y = RandomNum_First.Next(16, 235);
            int u = RandomNum_Sencond.Next(16, 240);
            int v = RandomNum_Third.Next(16, 240);

            int R = (int)(y + 1.14 * v);
            int G = (int)(y - 0.394 * u - 0.581 * v);
            int B = (int)(y + 2.028 * u);
            if (R < 0) R = 0;
            if (G < 0) G = 0;
            if (B < 0) B = 0;
            if (R > 255) R = 255;
            if (G > 255) G = 255;
            if (B > 255) B = 255;

            Color rgb = Color.FromArgb(R, G, B);
            return rgb;
        }