From what I've read there isn't too much at all for schule planes, at least not advanced or front line planes like what you're doing. Just standard paint. Blind flying (instrument flying) training planes had 2 broad RML 04 bands on the fuselage sides, usually within and under the call letters, forward and aft of the crosses but positions varied.
Some trainers had the undersides of their cowlings painted yellow and sometimes yellow rudders, but not as common practice. Also some had large white numbers on the tail. Mostly front line training was done in standard painted planes. In fact, I think all trainers were painted in the standard finish and markings for the plane in question.
Maybe you would be better off making something up since there aren't any standard schule markings? After all, it's your schule, not the Luftwaffe's
What would make them easy to ID in flight but not make them stand out too much?
but decided to try go for historical correctnes)
Linear Mode
