Ok I think I've worked it out - here's the pic (I hope)
I was really pleased with this one - even though I'm giving the fish away
I think the red tinge is gender specific but not sure whether male or female
This is the most dominant and meanest dawn - got to be male surely?
No, they all have white tips to their anal fins. It's the thickness of the black edging that is supposed to be the difference. Personally, I think it's the black at the top of the anal fin, next to the body, that is the difference. I have two with hardly any black there - and they both have the red tinge. Don't know whether they are male or female though. Just guessing by their behaviour