1. A composition for dyeing keratin fibers, containing at least one aqueous dispersion of particles of a hybrid film-forming hydrophobic acrylic polymer, at least one linear silicone block copolymer and at least one pigment. The composition of claim 1, wherein the linear silicone block copolymer is in particulate form in dispersion in an aqueous medium. The composition according to claim 1 or 2, in which the silicone block copolymer is obtained by a chain extension reaction, in the presence of a catalyst, from at least: - (a) one polysiloxane (i) having at least one reactive group and preferably one or two reactive groups per molecule； and- (b) one organosilicon compound (ii) that reacts with polysiloxane (i) through a chain extension reaction. 4. The composition according to the preceding paragraph, characterized in that the organosiloxane (I) is selected from compounds of the formula: in which R and R are independently from each other a hydrocarbon group having from 1 to 20 carbon atoms or an aryl group or a reactive group, and n is a whole a number greater than 1, provided that there is an average value between one and two reactive groups per polymer. 5. The composition according to the preceding paragraph, characterized in that the reactive group is selected from hydrogen； aliphatically unsaturated groups； hydroxyl group； alkoxy groups； alkoxy alkoxy groups； acetoxy groups； amino groups； and mixtures thereof. 6. The composition according to claim 4, characterized in that R represents a methyl group and R at the end of the chain represents a vinyl group. The composition according to claim 3, characterized1. Композиция для окрашивания кератиновых волокон, содержащая, по меньшей мере, одну водную дисперсию частиц гибридного пленкообразующего гидрофобного акрилового полимера, по меньшей мере, один линейный силиконовый блок-сополимер и, по меньшей мере, один пигмент.2. Композиция по п.1, в которой линейный силиконовый блок-сополимер находится в форме частиц в дисперс
