Male - easy to tell at that size what they are. Usually it's hard to tell visually the sex of a GT until the 4" mark. I was expecting a picture of a 1.5" GT when I saw this thread.
its all about the genes. some GT's don't colour up til the 5" mark, some people have fully coloured 3" males with little koks. depends on the parents.
and as for the behaviour it can vary a lot from cichlid to cichlid, I've never found GT's to be any more aggressive than say a JD or a jag, in my experience they mix pretty well. but again this is all just subjective.