Using Arctic Fox's Poseidon hair colour is a breeze. First, make sure your hair is pre - lightened to a cool - toned level 8 or lighter for the best results. Before applying the colour all over, do a patch and strand test to check for any allergic reactions. To apply, simply follow the DIY formula and spread the colour evenly through your hair. If you want a pastel baby blue look, mix Poseidon with a bit of Arctic Mist. And if your hair has some brassiness, add a dash of Purple Rain. After colouring, the hair dye is semi - permanent, so it will gradually fade. To maintain the colour, use a gentle, sulphate - free shampoo and avoid excessive heat styling. Also, protect your hair from direct sunlight as it can cause the colour to fade faster.