Should retain the majority of this colouration. As for sex it's tough to give an accurate i.d without a shot of it's sex organ, but post a pic with it's fiinnage spread and i'll do my best.

I thought that you could tell by the head bump and top fin...no? Or is that just with Midas?
My focus has been on africans for so long that I feel like a rookie when it comes to Americans.

The nuchal hump is by no means a good indicator when young, many of female will have a nice sized nuchal hump also. As for the finnage males will generally have extensions/trailers on the dorsal and anal fins, this is why i ask for that picture. Again, sexing Rd/Midas is most accurate by venting.

Could be a female.. Males get a some what more beefier body and the females stay slimmer.. She OR he should have already layed eggs by now.. They wil lay eggs regardless if a male is in the tank.. IF NO eggs then a young male.. RD don't get big Nuchal humps like the Midas do.. But it wil get bigger than that at spawning or right before she?? lays eggs.. Mine did..
Venting is the best way and can be done at this size.. if you can get a pic of the belly as in feed something right as she is at the front glass then get some pics as the underside faces you..

nice color

sweet fish