I haven't ever seen a yellow convict. I have a pink one and a striped one.
The low-down on Con's tho is they will eat a typical cichlid diet of flakes or pellets, I also feed my frozen bbs, frozen bloodworms, and frozen krill.
They can be very territorial, *especially* when breeding. And if you have a pair, they will breed like rabbits. The females with have orange on their bellies once they reach sexual maturity. Both of mine are females and have the orange color on them probably 90% of the time even tho there are no male cons with them.
I think once fully grown they are about 5-6".
Hope some of this helps!