how do I write custom themes

I have been looking into creating my own custom theme based on the glossy look and understand much of the xml language with one exeption, I can't figure out how it is defining colors in the field it says something like gtk[NORMAL]\2.5 (note this is not exact because my memory is not perfect and I am writing this from a windows computer so I have no way to check.) If someone could explain this to me or tell me how to get the info I need it would be greatly appreciated...