A method for coloring of cellulose in a supercritical CO2 medium by an uncharged hydrophobic dye, including at least the steps including of: (i) provision of cellulose fibers, (ii) placing the cellulose fibers in the presence of: a) an effective quantity of at least one uncharged mono organo-urea primer of formula R—NH—CO—NH2, where R represents a linear or branched, saturated or unsaturated, hydrocarbon chain possessing at least 3 carbon atoms, or a saturated or unsaturated cyclic hydrocarbon radical, which is bonded directly or via a methylene or ethylene group to a nitrogen atom, and if appropriate substituted under conditions conducive to the forming of a covalent carbamatic bond between the cellulose and the molecules of the organo-urea; and b) at least one hydrophobic dye in a supercritical CO2 medium, under conditions conducive to the immobilization of the dye on the fibers.