This washes out in 10 to 12 washes and contains no ammonia. Colour actually coats your hair, but doesn’t penetrate, so it fades with washing. It’s great if you are a first-time user or you just want to deepen or add a layer of colour to your natural tone. It’s not so great if you want a dramatic change in colour or you have a lot of grey.
Contains no ammonia but usually has a small amount of peroxide to open the hair cuticle so some colour penetrates. It lasts 12 to 28 washes, and is more effective than semi-permanent for darkening hair (but not as effective as permanent). It’s great for blending grey or enhancing your natural colour. But with demi-permanent, ‘if you have more than 50 percent grey hair, you might not get full coverage,’ says Luis Pacheco, a Toronto-based consulting colourist for Clairol. And since you’re not actually lifting out the hair’s natural pigment, ‘you can’t go much lighter than your own shade.’
The longest-lasting option, it won’t wash out. Instead, it grows out, leaving visible roots’you’ll have to touch them up every four to six weeks, depending on how fast your hair grows. Permanent hair colour frequently contains ammonia. If your hair is more than 50 percent grey or you want to lighten or darken it a few shades more than your natural colour, this is the type of hair colouring for you.