Most Helpful Guy
No polish and shorter length is my personal favorite. I don't like longer myself, but just about any color nail polish is fine if you want to wear it. Any shade of red is my least favorite, but I also don't like the color red in general.
When I was younger, with my first girlfriend, I was more adamant about the fact that I didn't like nail polish and it was a real point of contention for us. In my slightly older age I understand that a girl should do whatever makes them feel good. So I hate to sound cheesy or something here but you should do what makes you happy with your nails.