These are both quotes from Mr. Evil on the Atari forums.
Then you'd just have to code the GUI to have three sliders (RGB) and these would affect the constantcolour's properties, won't they? Then you'd be able to affect the colour of the car skins, witout discolouring things like glass or ads! Completely customisable skins and you won't have to include all of these pre-made skins! For hose with two or more colours to change just add extra sliders and extra constant colours and combiners!
How about using a ConstantColor, a Combiner and a neutral base texture instead of having a separate texture for each colour? It would greatly reduce the file size and allow all 16.78 million possible colours to be selected.
Make a base texture with all the coloured parts neutral (white/grey). Make a mask the covers everything except the coloured parts. Save the mask as the alpha channel of the base texture. Make a ConstantColor material (you can either make one in UEd and save it in a package or create one dynamically via UScript, I prefer making them in UEd myself). Use a Combiner to combine them. I don't know the exact settings you would need, just experiment.
Then you'd just have to code the GUI to have three sliders (RGB) and these would affect the constantcolour's properties, won't they? Then you'd be able to affect the colour of the car skins, witout discolouring things like glass or ads! Completely customisable skins and you won't have to include all of these pre-made skins! For hose with two or more colours to change just add extra sliders and extra constant colours and combiners!