All colours are beautiful ! You can say what colour is better because it depends of your skin tone and the face of the person. I like all colours but i have preference for the medium tones because it make more contrast with your face. Girls that wear a extra very light blonde like platinium blonde sometimes look sleepy or tired. Very dark hair like black sometimes make you appear more older.
Honestly it depends some girls look hotter with blonde hair, others will look better with brown, red, black etc. It all depends on her face, and genetics. And usually your naturally hair color is the best color for you.