The one is definitely a female as you can see the pink belly. The other looks like it has a little pink so I would say it may be a female as well but can't quite tell. People will tell you to look at the dorsal fins as the males will be higher and most of the time they are but not always and then people say to look at if the black spot is mottled with blue which is crap and almost totally unreliable and any other of a number of reasons but all you need to do is look and see if she has a pink belly. The female GBR will always have a pink belly which will get redder as she gets closer to breeding and the male does not. It's plain and simple. It kills me to see all these weird ways to tell if its a male which non are 100% reliable except for the pink belly.