W I S C H N E R

If you need a portable .NET solution for converting RGB to HLS and vice versa there are libraries around to do it. For Windows only using the Shell Lightweight Utility Functions is a simpler alternative.

[DllImport("shlwapi.dll")]
static extern int ColorHLSToRGB(int H, int L, int S);
[DllImport("shlwapi.dll")]
static extern void ColorRGBToHLS(int RGB, ref int H, ref int L, ref int S);
// RGB2HLS
ColorRGBToHLS(ColorTranslator.ToWin32(rgbColor, ref h, ref l, ref s);
// HLS2RGB
Color rgbColor=ColorTranslator.FromWin32(ColorHLSToRGB(h, l, s));