Since I have two PEW girls who are the same age, it can be hard to tell them apart. While they do have different personalities, if they're in the cage I can't really tell who's who. So what I do is I put food coloring on Miri's tail! It's completely safe for them and it lasts a while! Now I know that the one with the blue tail is Miri and the one without coloring is Bean!
The first picture is of Miri, the second picture is of Bean, and the third picture is them together! Sorry if the pictures aren't the greatest, they were the best pictures I could get. ( Rats don't exactly stay still for photos! XD )