Others will certainly agree, do yourself a favor and get some Vellejo acrylics, if acrylics are your paint of choice. Good paints, engineered for painting figures specifically and are also designed to be used with a paint brush. They go on nicely, though some (myself included) find advanced techniques difficult to master. I use them for base coats to paint oils over and they work splendedly in that capacity as well.
As for color, as was mentioned above, the web is a good source, though most of the photos will be black and white. The Luftwaffe used a blueish gray color that could be achieved with a mix of Testors flat blue and Testors flat gray. Check you LHS for Dragon or Tamiya figure sets with Luftwaffe figures in them and see what colors they used on the box art.
Osprey and Squadron/Signal also have great books with lots of pics and color plates that would be of use too. Your LHS would likely have them in stock and you could just browse through them to get the color ideas you need without buying them, though owning them isn't a bad idea.
I'll echo the idea that it's not rocket science. Every identical article of clothing wears and fades differently, so four guys wearing the same uniform will show differences in color. Also, uniforms were made by more than one factory and fabrics and dyes differed from one factory to another. Throw in wear and tear too. So you've got a lot of room for error here.