Well as far as agression goes, I have some females that are more aggressive than my males. One can't even go into the community tank b/c she is so mean. I'm not sure on answers as to rasboras or others. I'm too scared to mix anything up. If you are worried about colors I think you'll be surprised at how cute and colorful the females can be. My tank has a ton of color in it, and is my favorite tank. I get comments on it all the time, and people are amazed that the occupants are just simply female bettas. Maybe someone else can help you with things that are compatible with girls. Mine would surely kill anything that I tried to put in their tank.