In the Blue's, if you look at a tank full; the undamaged males in general will show one larger claw. I state undamaged because if a male lost main claw in fight, etc. the replacement claw will be smaller for a few molts and it will look like a female. I can't tell; but experienced keepers can sex some crayfish species by observing difference between male and female vent location.

Molting is very cool to watch. The old molt will separate dorsally and the crayfish will kick it off body by moving tail. Once it's off, the crayfish will do "body stretching" before new skeleton hardens, and at that moment you can actually see it grow .