What rainbow color should I put in my hair and where?

My hair is pretty long with layers. It is dirty blonde. I got highlights a year ago and they are midway down my hair. Which color would look the best? (red, orange, yellow, green, light blue, dark blue, purple, hot pink) where should I put it in my hair? Underneath or on top. Oh and I am only doing on small streak. Thank you for the help!! : )