I love both red and black hair. (Neutral to all other colors) And I don't really like black, brown and red eyes. (As in albinism) So I could say I like lots of combinations. If I try to force myself to think of a killer combination, I probably would say red hair with hazel eyes.
Difficult to say. I find a variety of combinations attractive. Red hair and blue or green eyes on women (not so much with men). Dark hair and light (blue or green) eyes on men. But really, it depends on the person... Variety is the spice of life.