A method of colouring keratinous fibers comprising contacting the keratinous fibers sequentially with a pre-treatment composition and a colour developer wherein : i. the pre-treatment composition comprises: (a) 0.5-25% by weight of an iron salt at a pH below 2 including 0.5-5% by weight of a reducing agent (b) a buffer effective in the pH range 3-6 and (c) a penetration enhancer comprising one or more solvents having Hansen solubility parameter δh between 1-10 (MPa) 1/2 and δp between 10-25 (MPa) 1/2 wherein the component (b) is mixed with (a) or (c) not more than 360 minutes prior to contacting the keratinous fibers and ii. the colour developer is selected from one or more of hydrolysable tannin or its breakdown products or derivatives or a mixture thereof obtained from a natural or synthetic source, where the sequence of contact is in any order.