Lime Crime Unicorn Hair Semi-Permanent Fantasy Hair Colour – Chestnut. Chestnut is a deep maroon brown shade which provides full coverage! These new shades can be used on unbleached hair! Works best on pre-lightened hair. You cannot dye hair lighter – if your hair is darker than the colour you are trying to achieve then you must lighten first. Full coverage dyes do give a nice tint on most natural hair colours. Unicorn Hair, hyper-performance hair colour from Lime Crime that leaves hair feeling silky-smooth and smelling like a meadow! Lime Crime Unicorn Hair is a 100% cruelty-free and vegan hair dye.