Process for coloring fibrous structures

A process for coloring a fibrous structure consisting essentially of fibers selected from the group of natural fibers, semi-synthetic fibers and synthetic fibers which comprises applying a solution of a coloring agent and a methylol compound derived from formaldehyde, the amount of said methylol compound being about 0.7 to 30% by weight of said solution and being about 1 to 20 times the weight of the coloring agent, to the fibrous structure, heat-treating the fibrous structure at 100.degree. to 220.degree. C for 0.1 to 10 minutes and then treating the fibrous structure with a reducing agent selected from the group consisting of hydrogen, hydrogen iodide, hydrogen sulfide, lithium aluminum hydride, sodium borohydride, carbon monoxide, sulfur dioxide, thiourea dioxide, thiourea sulfite, sodium sulfide, polysodium sulfide, ammonium sulfide, alkali metals, magnesium, calcium, aluminum, zinc, iron (II) salts, tin (II) salts, titanium (III) salts, chromium (II) salts, aldehydes, saccharides, sodium bisulfite, Na-sulfoxylate formaldehyde, modified primary zinc salts of formaldehyde sulfoxylic acid and a hydrosulfite said reducing agents being used in an amount of 0.05 to 5% by weight based on the weight of the fibrous structure.