wow, if you can't tell what an adult male looks like, perhaps you shouldn't be breeding? there are a lot of sites which show how to sex a gecko, even before sexual maturity when it is outwardly/visibly obvious.
-----
4.1 snakes, 4.6.1 crested geckos, 0.1.1 gargoyle geckos, 0.0.2 red-eyed tree frogs, 2.0 devon rex cats, 1.0 betta, 0.1 sun conure, 1.0 peachfaced lovebird, 2.0 lineolated parakeets