milk_shake Direct Colour Bluemilk_shake Temporary Blue Colour Treatment. From deep blue to subtle stonewash, denim is the newest way to wear your hair, according to top British hairdressers. milk_shake blue direct colour is a cosmetic colour that can be used at home or in the salon to colour, condition and protect the hair. The hair colour is temporary and has the ability to correct difficult technical hair problems. Find out how to create a variety of denim washes in the 'Use'