Anyone with lightened, highlighted, or grey hair that's pulling yellow or brassy instead of staying cool-toned. It's used both by stylists as an in-salon toning step and by the person at home for maintenance between appointments, so it's not a professional-only product — it just happens to also be a salon tool. It's not useful on hair that isn't already lightened or grey, since there's no yellow pigment for it to cancel.

What separates this from a typical purple shampoo is that the toning pigment and cleansing surfactants are built to work together at a specific pH (4.5), so the colour deposit happens fast enough to use as an in-salon step rather than something that only works after sitting for 15-20 minutes. At home, that same speed means a couple of minutes of extra time during a normal wash is enough to keep brassiness in check between salon visits.

In-salon correction: apply to wet hair, leave on for up to 5 minutes depending on how much yellow needs neutralizing, then rinse thoroughly; wear gloves and protect skin, clothing, and surfaces from staining. Home maintenance: use 1-2 times a week to hold the cool tone. Using it daily gives the strongest tonal deposit but isn't necessary for most people and raises the risk of over-toning.

• Cancels yellow and cleanses in one step instead of needing a separate purple shampoo plus a regular shampoo
• Sulfate-free base is gentler on freshly lightened hair than an SLS shampoo
• Works for both in-salon correction and home upkeep

• The concentrated direct dyes can stain skin, nails, and light towels or shower surfaces without gloves and careful rinsing
• Leaving it on longer than needed can over-tone hair (push it too ashy/purple), so it takes some judgment on timing rather than a fixed rule
• Not usable on hair that isn't already colour-treated or grey — there's no brassiness for it to correct