This product is great for a one-time pop in your hair. My favorite of them is the pink because it looks the best in my blonde hair. It may have a harder time showing up on dark hair, but I can't confirm it because I haven't had a personal experience. Overall I think it's a great product.
Helpful if you have light hair
I have strawberry blonde/red hair, so the colors don't have a hard time showing up. I have this in green and I love it because its an absolutely perfect shade of green. It stays put all day, and I didn't have any staining on my clothes. my fingertips got a bit green, but everything else was stain free. If you have dark hair, i'd skip these, because odds are they will not show up in your hair. If you have lighter hair, though, these are a fun way to mix up your normal hair routine.