My opinion still stands on crossbred of RTGxGreen. Coloration on scales remind me of Green Aro. Finnage color reminds me of an RTG.
1. Just an FYI, not all RTG have RED tail. Most either have orange or really dark orange tail. The enviroment and diet will affect the color on it's tail. So if an RTG that has dark orange tail, isn't an RTG?
2. High back have gold shine up to the 5th scale level. Not 3rd or 4th. Like you said, it doesn't have color. It can't be an RTG. An RTG at that size should have thin gold frame on the scale, even if it's kept in a light tank.
3. Grade 2 Reds look similar to Grade 1 Red when young. Dorsal, Caudal, and Anal fin is Red. The Aro in the O.P has greyish color on the Dorsal fin.
Oh, I think I'm color blind.

I don't see red but I see orange.