In paintings on an image search, he has brown hair.
He has light brown hair
gray
He had red/brown hair.
Brunette
Louis tonlinsons hair used to be brown but it's gone fair now
he's blonde
Bright orange and purple
Reddish-Brown.dark brown
Emma Roberts natural hair colour is a light brown i guess you would call it dirty blonde.
His favourite colour was blue they predict
There is no universal "sexy" hair colour. Hair colour is a personal preference. Your hair colour should be a similar shade to your eyebrows and should compliment your eyes. Ask a professional hair stylist what colour suits you.