Abstract: The present invention relates to an oxidative hair colouring and bleaching composition comprising an oxidizing agent, a source of carbonate ions, an alkalising agent, and specific dyes, as defined herein below, utilised at pH 9.5 and below which improve colour delivery and intensity, excellent dye deposition and colour and improved grey coverage, particularly for dark shades such as brown or black. Moreover, the compositions of the present invention also exhibit low odour and deliver a high level of lift and lightening equal to the currently utilised ammonia/peroxide systems, whilst reducing the concentration of peroxide and reducing the hair fibre damage.