I've found the Vallejo Air to have a good color range for German armor, though fair warning: the surface primer colors and the Air colors are different for Dunkelgelb. Surface primer is much darker. Vallejo paints do have RAL numbers on the bottles though, so that's handy.
That being said, I concur with the replies here - there was so much color variation depending on the date, the unit, how long the vehicle had been in the field, what the paint was mixed with, where the vehicle had been serving... I'd say just find a correctly-named or close-looking color you like, and go for it.