15 Rainbow Hair Trends That Dominated Salons in 2015

If you're a brunette and don't want to subject your strands to the harsh bleaching process (but still want to get in on rainbow fun!), you should try the oil slick trend. Deep tones of green and purple dye are layered on top of dark hair to create an almost iridescent effect, like that of a puddle of oil in a parking lot. Bonus: the rich shades last longer than pastels.