I think they stopped using Feldblau pretty early on.
Well, the Luftwaffe Field Divisions never really stopped wearing them per sé, but after being turned over to the Heer in late 1943 the uniform items to replace broken and used ones that would be issued would be feldgrau. So they would gradually phase out the feldblau stuff, but never had time to do it completely.
Didn't find anything solid on the HG PzKorps, but since that was never turned over to the Heer, I suspect that they would retain the Luftwaffe uniforms simply as a matter of being distinct.
In any case, I think having them all wearing feldblau and splinter camo is not straying too far from history.