Hahaha... Luciana is asking about the color. I thought they were golden agouti cause I remember seeing another pic of them. Golden agouti are brown with black ticking and black eyes. Grey agouti are grey with darked tricking and black eyes. REW/PEW = Ruby Eyed White/Pink Eyed White. They both look very similar, I think there's a difference in the eye, but I've never found good info about it. They are genetically different, though, that's why they separate the names. They are basically white with red eyes.
About the sexing... do you have a transparent bowl? Maybe you can put them there and let them walk, and look underneath. I've seen mice people doing it and it works... I've never seen it or tried it with gerbs, but it might work.