Blue shampoo

They don't correct the same tones. Blue neutralises orange tones, the ones that come out when you lighten a brown, dark brown or dark blonde base. Purple neutralises yellow, the kind you get on already light blondes and polar blondes. If your hair pulls orange, go for blue. If it pulls yellow, go for purple.

No, and that's normal. Blue corrects the orange tones created by lightening. On a natural, un-lightened brown base, there's no orange to correct, so you won't see anything. On the other hand, if your highlights or balayage on a brown base are turning orange, that's exactly what it's made for.

1 to 3 minutes depending on the intensity you want, then rinse thoroughly. Don't go beyond 3 minutes: after that, the result can turn the hair fibre grey instead of correcting it.

1 to 2 times a week, no more, instead of your usual shampoo. Focus on the lengths that are turning brassy, then carry on with your normal routine.

Not in the same wash. These are two correctives for two opposite tones, and using them both at once can dull your blonde. Pick the one that matches the tone you're dealing with right now. If you have both shades in different areas, alternate from one week to the next.

It's formulated with 86% ingredients of natural origin, including ginseng, wheat proteins and betaine that help keep hair soft. Like any pigmented shampoo, you don't use it every day: 1 to 2 times a week is plenty.

About 3 months with 1 to 2 uses per week. 250 ml bottle.

Yes. The spray lightens, the blue shampoo corrects the tone that shows up along the way. They're made to work together: you lighten with one, you keep a cool blonde with the other, 1 to 2 times a week.

No. Its blue pigments neutralise orange tones on already lightened hair, without changing your starting colour. The result depends on your base: the lighter your lengths, the more visible the correction.