They should color up. Those on the previous photos are about 5 years old.
But I have some that are just a few months old, here are two of the young ones together with two adult ones:
Young ones - one is in front and another on the right (seen together with its reflection in the glass, near badis) - are about 1/3 of the size of the adults, their stripes are more white than gold, tail fin is transparent. The one in front seems nearly as big as adults simply because it is much closer to the camera.
I used to feed them various frozen Hikari food (brine shrimp, spirulina brine shrimp, daphnia, bloodworms, mysis shrimp) and NLS pellets (1-1.5 mm size). Occasionally live blackworms. They were gladly eating all of this (mysis shrimp was probably the least favorite though).
A few months ago I've started culturing grindal worms and since when it is mostly grindal (and fruit fly larva that unfortunately grows in my grindal cultures in abundance) exclusively simply because now they refuse to eat frozen food and pellets - the same food they were happy with for years before...
BTW, tank water is prepared from RO to achieve 0.25 dKH and 2 dGH.
In the tank TDS ~ 80-110, pH ~6.4, temperature ~76F.