Which armies are you interested in? There is a lot of info on the French and the Dutch armies in the booklets sold originally by Raider, written by Alan Sapherson. I think they are still available from Caliver/Partizan. He also wrote a series on the British Army from James II through William but there is less info available on uniforms there. You would probably find his stuff on Abebooks as well, second hand.
There is a lot of stuff on the French, especially on flags. on the Net but also on the history of various regiments which survived into the 18th Century. Try places like here:
http://www.kronoskaf.com/syw/index.php?title=French_ArmyIts really about the period of the Seven Years War but it gives regimental histories and shows their standards (which, for surviving regiments, rarely changed). For other armies, however, you have to go to book(lets) like Sapherson's. His one on the Dutch, for example is really excellent with regimental info, uniform colours and often standards as well.