The newest trend is no longer pure rainbow hair. As if it would've ever made it to my town. However, here's a trend that might be do-able without being called "emo", "grunge", or "weird".
The newest trend is mixing your natural hair with some rainbow strands.
These were my personal favorites because when you decide to rainbow color your hair, you don't have to fully commit. If you want to start with just a few strands, do so. Then proceed, if you're digging it.