It's hard to tell in these pics but I THINK you have two females and a male. They will get more color the longer they're in your tank. The more comfortable and the older they get, the more color they'll become. My adult male gets really colorful when he's "frisky". Not only does the yellow get brighter, but his blue get so dark it almost appears purple. I also have Marci Rainbows (Melanotaenia marci), and as they get older their whole back turns almost a florescent orange.
The third one certainly looks like a male. The first looks female. The second is harder to tell. It's color is more subdued, but it's top fins are close together like in males. It has been a while. What do they look like now?
Rainbows are really fun to watch as they grow and change colors.