Seriously? 12 views and no replies? I know that SOMEONE has figured this out; as many non-default models feature it.
If you dont get what Im asking, look:

In the above picture, parts of the vehicle are grey instead of white. pretty basic/nice. But when you paint it...

That grey turns to a darker red shade rather than it being red and grey. This is the issue I am having, when I paint a model, any colors that are non-default materials stay the same. How do I make them change shades?