Unless you've got Viking-style blonde hair already, yes. Even if you're just going for an ombre color on the ends, a Pastel color won't show up on anything darker than platinum blonde. Even medium blonde is too dark to show true pastel tones. If you want to add a very subtle tint color to your darker hair, consider going with the Vibrant line instead. Remember - the darker your hair is, the more subtle your results will be.