Very bright!
I was hesitant to buy this after reading all of the reviews that said the colors were faint in dark hair.  Maybe it's the way I applied it, I don't know, but I have very dark hair, and people were amazed at how vibrant and bright every color was.  I made a rainbow in my hair and sealed it with hairspray, and it stayed very bright for several days until I washed it.  My tip is to apply heavily and seal with firm hold hairspray, and you'll be very happy with the color.
Rating: 5 stars