Every rational dua is permissible.
One person who have brown eyes cannot make dua that Allah would change his eyes color to blue. This doesn’t make sense.

I was wondering about your opinions on making duaa to Allah about your looks, f.ex. to become taller, for your hair to be more beautiful and simply ask Allah to make you more attractive (specially because you want to satisfy your future spouse). Is it completely stupid, or is it just ok?