I made a (not very good) one ages ago. It explains it well enough, though.
![[Image: hueshift2go9.png]](http://img151.imageshack.us/img151/8166/hueshift2go9.png)
A little bit confused with that saturation and Lum?.
Saturation is how 'bold' a colour is. The red that you get in MSPaint is a Red hue with maximum saturation. A colour with no saturation is in greyscale.
Luminosity is how 'bright' a colour is. Maximum Lum. is White, no Lum is Black.
The second image uses colours that are all the same Lum. as the palette in the original, but the hue stays the same. The third image has all colours the exact same saturation and brightness, but simply changes hue to represent light and dark. Moving the hue towards yellow makes the colour 'lighter'. Moving the hue towards purple makes the colour 'darker'.