For virgin or all-over coloured black to dark brown hair (levels 1 to 4) that shows red undertones. It is a weekly maintenance mask for dark bases.

Do not use it on white or grey hair, or on hair lightened to level 5 or lighter by colour, lightener or the sun, because the blue-green dyes can leave a greenish hue.

Brunettes deal with warmth too, but on dark hair it shows up as red rather than yellow. Dark Envy places blue-green dyes, which sit opposite red on the colour wheel, in a nourishing mask, so a few minutes once a week keeps dark colour looking deep and cool instead of coppery, and the hair comes out conditioned and shiny.

• Shampoo and rinse.
• Wearing gloves, apply to wet hair, avoiding the scalp.
• Leave on for up to 5 minutes, depending on the cooling effect you want.
• Rinse thoroughly and style as usual. Use weekly.
• Results vary with the porosity of the hair.

Pros

• Blue-green direct dyes neutralize red undertones on dark bases
• Conditions like a mask while it tones, leaving a cool, glossy finish
• Short processing time of up to 5 minutes
• Vegan formula

Cons

• Only for levels 1 to 4; it can turn grey, white or lightened hair greenish
• Gloves are needed and the scalp should be avoided, as it can stain
• Discontinued by Matrix, so supply is limited