If I remember right, they are like JDs in the fact that females get a Blue beard on the lower part of their faces from thier eyes sweeping around to her gill plate.
If this is true, I am sure a GT owner will chime in soonTM. But going by this assumption the first fish is male, the skin around the area mentioned is his normal brownish color of that area. The second fish/pic (The fish on the right, not the out of focus one on the left) looks female, if you zoom in you can see that the skin in area is blue. Finally the third looks to be male as well.
