Most colors won't even highlight dark hair, except for Violet, Plum and Midnight Blue. The reds wash out the quickest, 1-2 weeks, looking the nicest as they fade. If you want a true red, we recommend Pillar Box, Fire, Flame. The blues are next in the fading factor, 2-4 weeks. The lighter blues will tint to the greener side unless you bleach your hair first.
Purples tend to stay in the longest.
Yellows are tricky. Evi-Lynn just started using yellow recentely, mostly as stripes. The effects turned out pretty cool. Recommended that you have bleached hair first in order for the yellow to look good. 4 Evi-Lynn used it once and will never touch it again.