Red and green
They're opposite and complementary colours (on the colour wheel) so if you imagine them mentally (which is what most people do with descriptions), they looks much more vibrant and lush...hence more attractive.
red hair and green eyes
blue eyes are getting really common in real life and books and you don't see or hear about many people with green eyes
also i think it should be like a bright red like crimson to make the eyes stand out more
I think green eyes, especially if they are a vivid emerald green. Such an outrageous hair colour (unless it is dyed) suggests a mysterious, perhaps in human character. She should sound very pretty if you describe her right.
Hope this helps.