For all livebearer(i.e. guppies, mollies, platys) Males and females have different anal fins. The female has the normal fin that you would see on most fish but the male has a modified one called the gonopodium which helps in the transfer of sperm into the female. You will most likely be able to...
The fish's color is just changing a bit, kinda like how a baby's hair is usually blonde and when they get older it gets darker. There is nothing to worry about!;)