Well you've been 'blonde' for a few weeks now and just love your new look, but guess what ? In certain lights you can see that the hair is starting to look a strange shade (?). This known as the hair looking 'brassy'. It's basically the stage where the dye you put in on the second stage is fading, but there is still some remaining, and the 'yellowness' of your hair underneath are mixing together and giving a 'funny' look to the hair. Also by this time your hair will have been exposed to the elements/car fumes/smoking etc and this also dulls the hair down. The over-all effect can be quite sludgy looking.
Blue shampoo is the solution!!
Sounds weird doesn't it ? But it is all to do with 'opposite' colours on the colour spectrum.
The opposite of yellow is purple/violet and using a purple shampoo will effectively neutralise all the yellow 'tones' in the hair. It DOES work honest. In fact there are a number of products specifically designed for this problem and what they do is deposit a tiny bit of 'purple-hued' pigment in the hair to calm the yellow tones down. It also works for natural blondes in need af a bit of a boost, as well as highlights.
As a blonde i have use a couple of them, so I can surely tell you that they work. I have use
Loreal Serie Expert Silver Shampoo