Good Dye Young Semi-Permanent Hair Colour Narwhal a salon-quality dye that does not damage hair and will last 16-24 washes. Narwhal is a true teal with soft green undertones. This shade is the most magnificent teal, almost too good to be blue. This dye uses salon-grade pigments with hydrating ingredients in a non-toxic cream base, ensuring bold, bright colour payoff. This semi-permanent dye works like a conditioning hair mask and the easy application creates stunning results. Most vivid on level 9+.