I'm not too familiar with non-African cichlids. I would guess an American cichlid of some sort. How long are they? I feel like they are still young, other wise there would at least a little color on them. Could you try getting close up pictures of each fish?
I really don't know, but 3ish inches probably means their juveniles. Try looking up "brown acara". The rounded tail looks similar and the head looks about right. It's hard to say, you might have to wait till they mature a bit.
Hi all just a follow up to this, this morning they were both a lovely yellow colour and I think I have a male and female. One is cleaning one of my flat rocks so fingers crossed for spawning. So yes they are Rainbow Cichlids