Materials are coloured by dyeing or printing them with a dyestuff derivative (obtainable by the process described in Specification 480,358) of the general formula R1-O-R2 where R1 is the residue of a dyestuff containing at least one hydroxyl group and R2 is an acyl residue containing at least one group which forms a salt with a base (including a group in the form of such salt) or at least one quaternary ammonium group, and subsequently or simultaneously treating the materials with a saponifying agent, preferably one having an alkaline action, e.g. alkali metal hydroxides, carbonates or phosphates. The dyestuff derivatives may belong to the azo, anthraquinone, triphenylmethane, azine or oxazine series. The process is applicable to the colouring of animal or vegetable fibres, e.g. wool, silk or cotton, or artificial fibres, e.g. regenerated cellulose or cellulose derivatives, or artificial masses. If there are used derivatives of dyestuffs capable of forming metal complexes, a treatment with an agent yielding a metal may be applied before, during or after the saponification on the fibre, in the dye bath or in lacquers or artificial masses. In examples: (1) wool is dyed with the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff a -naphthylamine --> b -naphthol from a bath containing sodium sulphate and acetic acid, and is then treated in a solution of common salt and ammonia, yielding a Bordeaux dyeing; (2) cotton is dyed with the reaction product of benzoic acid-3 : 5-disulphochloride on the azo dyestuff benzidine \sQ b -naphthol from a bath containing sodium carbonate and sodium sulphate, and is then treated in an alkaline solution, e.g. caustic soda, producing a violet dyeing; (3) acetate artificial silk is dyed with the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff p-anisidine --> p-cresol, with subsequent addition of ammonia to the bath, to produce a yellow dyeing; (4) cotton fabric is printed with a paste containing the reaction product of benzoic acid-3 : 5-disulphochloride on the azo dyestuff a -naphthylamine --> b -naphthol, neutral starch tragacanth thickening and acetic acid, and is then steamed and drawn through a caustic soda solution, yielding a Bordeaux red print; (5) a printing paste containing the reaction product of benzoic acid-m-sulphochloride on the azo-dyestuff 4-chloro-o-toluidine --> b -hydroxynaphthoic acid p-methoxy-o-toluidine, neutral starch tragacanth thickening, sodium chlorate and acetic acid is employed in the process of (4) to give a red print; alternatively the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 4-chloro-2-aminophenol --> p-cresol is employed, and the print is treated with an alkaline copper solution. Samples have been furnished under Sect. 2 (5) of materials dyed or printed as follows: (I) silk is dyed with the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 1-chloro-4-methoxy-3-aminobenzene --> 2 : 3-hydroxynaphthoic o-anisidide from a bath containing acetic acid with subsequent addition of sodium acetate, producing a yellowish-pink dyeing; (II) wool is dyed with the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 4-nitro-2-toluidine --> 2 : 3-hydroxynaphthoic anilide from a bath containing sodium sulphate and acetic acid with subsequent addition of sodium acetate, yielding a red dyeing; (III) cotton is dyed with the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff monobenzoyl - 2 : 5 - diaminohydroquinone diethyl ether --> 2 : 3-hydroxynaphthoic anilide from a bath containing sodium sulphate and acetic acid with subsequent addition of sodium carbonate, producing a blue dyeing; (IV) cotton is dyed with the reaction product of 4-chloromethylbenzoyl chloride and pyridine on the azo dyestuff 2-methyl-4 : 41-diamino-5-methoxyazobenzene \sQ b -naphthol from a bath containing sodium chloride, and is then treated with caustic soda lye to yield a violet-blue dyeing; (V) wool is dyed with the reaction product of benzoic acid-m-sulphochloride on 21 : 41 - dinitrophenyl - 1 - amino - 8 - naphthol from a bath containing sulphuric acid and sodium sulphate, and is then treated with sodium acetate solution to produce a yellowish-brown dyeing; (VI) cotton is printed with pastes containing (a) the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 3-chloraniline --> 2 : 3-hydroxynaphthoic anilide, urea, resorcinol and neutral starch tragacanth thickening, and (b) tetrabromindigo, sodium sulphoxylate-formaldehyde and potash thickening (wheat starch, tragacanth thickening, British gum, potassium carbonate, glycerine and water), and is then treated in the Mather-Platt apparatus and drawn through a solution of sodium hydroxide and potassium ferricyanide; an orange and blue print is obtained; (VII) cotton is printed with pastes containing (a) the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 4 : 41-dichloro-2-amino-1 : 11-diphenyl ether --> 2 : 3-hydroxynaphthoic o-anisidide, thiodiglycol ether and neutral starch tragacanth thickening, and (b) Cibanone Green G double paste, potash thickening, sodium sulphoxylate-formaldehyde and urea, and is then treated as in (VI) to produce a green and red print; (VIII) cotton is printed with pastes containing (a) the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 2 : 5-dichloraniline --> 2 : 3-hydroxynaphthoic o-anisidide, thiodiglycol ether and neutral starch tragacanth thickening, and (b) Indigosol O4B, glycerine, neutral starch tragacanth thickening, ammonium sulphocyanide solution, sodium chlorate solution, ammonium vanadate solution and ammonia, and is then treated as in (VI) to yield a scarlet and blue print; (IX) cotton is printed with a paste containing the dyestuff derivative of (VIII) (a), thiodiglycol, neutral starch tragacanth thickening and zinc oxide, padded with an aniline black solution containing aniline hydrochloride, tragacanth thickening, aniline, sodium chlorate and potassium ferricyanide, and is then treated as in (VI) to produce a scarlet reserve print on a black ground; (X) cotton is treated with a solution of the quaternary ammonium compound from dimethyl sulphate and 1-stearoylamino-4-dimethylaminobenzene, printed with the paste of (VI) (a) and then treated with caustic soda lye; (XI) cotton is impregnated with a solution of the dyestuff derivative of (VIII) (a), thiodiglycol and starch tragacanth thickening, printed with a paste containing tetrabromindigo, British gum, glycerine, potassium carbonate and sodium sulphoxylate-formaldehyde, steamed and treated with caustic soda solution, producing a blue effect on a red ground; (XII) cotton is printed with the paste of (VI) (a) and with a paste containing Chrome Azurol S, neutral starch tragacanth thickening, acetic acid and chromium acetate, steamed and treated with caustic soda solution, yielding an orange and blue print; (XIII) cotton is printed with a paste containing the reaction product of benzoic acid-m-sulphochloride on indigo, the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 3-chloraniline --> 2 : 3-hydroxynaphthoic anilide, thiodiglycol and neutral starch tragacanth thickening, and is then treated in the Mather-Platt apparatus and passed through a caustic soda solution to yield a brown print. The Specification as open to inspection under Sect. 91 comprises also reference to the use, for the saponification, of acids and of the following additional alkaline compounds: alkaline earth metal hydroxides and alkali borates. Reference is also made to the use in example (1) of the reaction product of 4-chloromethyl-1-benzoyl chloride and pyridine on the azo dyestuff a -naphthylamine --> b -naphthol, and in example (2) of the reaction product of 4-chloromethyl-1-benzoyl chloride and pyridine on the azo dyestuff benzidine \sQ b -naphthol. In additional examples: (1) material is printed with the paste employed in sample (VI) (a) above and a paste containing Rapidogen violet B, caustic soda, turkey red oil and neutral starch tragacanth thickening, and is then subjected to acid steaming followed by treatment with caustic soda solution, producing an orange and violet print; (2) cotton is printed with a paste containing the reaction product of benzoic acid-m-sulphochloride on the azo dyestuff 2 : 5-dichloraniline --> 2 : 3-hydroxynaphthoic o-anisidide, butyric amide (alternatively the cotton is first impregnated with butyric amide), and neutral starch tragacanth thickening, and is then treated as in sample VI to yield a scarlet print; (3) mercerized cotton fabric is impregnated with piperazine solution, printed with the paste of sample VII, and then treated in the Mather-Platt apparatus to produce a red print through the saponifying action of the piperazine; (4) cotton is foularded with a solution of the reaction product of benzoic acid sulphochloride on the azo dyestuff 2 : 5-dichloraniline --> 2 : 3 - hydroxynaphthoic o - anisidide, thiodiglycol and starch tragacanth thickening, and then passed through the Mather-Platt apparatus and through a caustic soda solution to yield a scarlet dyeing; (5) cotton is impregnated with the solution of the preceding example, printed with a printing colour containing sodium sulphoxylate-formaldehyde, and developed as in the preceding example, producing a white effect on a red ground; (6) cotton is printed with a paste containing the reaction products of benzoic acid-m-sulphochloride on the azo dyestuffs 4-(41-methyl)-phenoxyacetylamino - 2 : 5 - diethoxyaniline --> 2 : 3-hydroxynaphthoic anilide and 3-chloraniline --> 2 : 3-hydroxynaphthoic anilide, thiodiglycol and neutral starch tragacanth thickening, and is then treated as in the preceding examples to yield a brown-violet print; (7) the first of the dyestuff derivatives of the preceding example is replaced by the r