//把十六进制颜色转化为color对象
ColorTranslator.FromHtml("#FF0000")
或 ColorTranslator.FromHtml("Red");

//把color对象转化为十六进制颜色
ColorTranslator.ToHtml(Color.FromArgb(255,255,255))
或 ColorTranslator.ToHtml(Color.Red);

//十进制转二进制
Console.WriteLine(Convert.ToString(69, 2));
//十进制转八进制
Console.WriteLine(Convert.ToString(69, 8));
//十进制转十六进制
Console.WriteLine(Convert.ToString(69, 16));
//二进制转十进制
Console.WriteLine(Convert.ToInt32(”100111101″, 2));
//八进制转十进制
Console.WriteLine(Convert.ToInt32(”76″, 8));
//十六进制转十进制
Console.WriteLine(Convert.ToInt32(”FF”, 16));

string color_s = ColorTranslator.ToHtml(g.Pen.Color);
color_s = color_s.Substring(1, color_s.Length - 1);
g.Pen.Color = ColorTranslator.FromHtml("#"+Convert.ToString(Convert.ToInt32(color_s, 16)+40000, 16));

Color Color1 = System.Drawing.ColorTranslator.FromHtml("#EEEEEE");
Color Color2 = System.Drawing.ColorTranslator.FromHtml("red");
  
/*
** Convert back:
*/
  
string Color1a = System.Drawing.ColorTranslator.ToHtml(Color1);
// --> "#EEEEEE"
  
string Color2a = System.Drawing.ColorTranslator.ToHtml(Color2);
// --> "Red"
  
string Color2b = String.Format("#{0:X2}{1:X2}{2:X2}", Color2.R, Color2.G, Color2.B);