Bob,
Welcome to the Forums and the hobby!
Changing paint for scale effect has, as Rick said, been a much talked about technique. There are even published ratios giving the proper amount of white that should be added to various colors for various scales. Doing so is supposed to duplicate the effect that atmosphere has on or perception of colors. Some modelers believe it is necessary, others don't, and as armornut said, there are many variables in the appearance of paint. My suggestion is experiment until you find what you like, what looks right to you.
Happy landings!