New Post: Index color and RGB color

using (MagickImage image = new MagickImage(@"E:\Development\DOTNET\PCXEditor\RGBEditor\18975253ee.pcx"))
{
  MagickColor target = new MagickColor(128, 118, 118);
  MagickColor fill = new MagickColor(100, 105, 110);

  image.Opaque(target, fill);

  image.ClassType = ClassType.Pseudo; // Or use the 'Quantize' method if you want more control.

  image.Write(@"E:\Development\DOTNET\PCXEditor\RGBEditor\1897525311-changed.pcx");
}