In a coloured plastic mass or coloured mass capable of conversion into plastic condition made from cellulose derivatives, natural or artificial resins or waxes, free from oil and containing if desired solvents which are not water-soluble alcohols, there is incorporated a complex metal compound of logwood extract. Suitable metals are chromium, copper, iron, cobalt, nickel, aluminium, manganese, zinc, vanadium, titanium, tungsten, or molybdenum. The metal may be used as hydrate or as salt with an inorganic or organic acid, or as a complex compound with ammonia or pyridine, or as a complex metal compound of logwood extract, and the treatment of the logwood extract may be effected in acid, neutral or alkaline medium. Oxycarboxylic acid, e.g. tartaric acid, formic acid, pyridine, or a salt of an inorganic or organic acid may be present during the formation of the metal compound. More than one metal may be used. The base of the plastic mass may be a cellulose ester or ether, copal, amber, shellac, colophony, carnauba wax, ozokerite, rubber, balata, guttapercha, casein, condensation products of aldehydes with phenols or aromatic amines, or with acid amides, or of polybasic acids with polyhydric alcohols, or polymerization products such as vinyl resin, styrene resin, or acrylic acid resin. The colouring matter may be incorporated by grinding solids together, and may, if desired, be produced in the sheet to be coloured. A fatty acid of high molecular weight, a filler such as barium sulphate, zinc oxide, or titanium oxide, or a softening agent or plasticizer, e.g. tricresyl or triphenyl phosphate, glycerine or castor may be added. In an example, 3 parts of the chromium compound of a highly oxidized logwood extract are ground during 4 hours in a roller mill with 8 parts of tricresyl phosphate and 2 parts of butyl acetate. 90 parts of commercial nitrocellulose lacquer are added and grinding is continued until dispersion is homogeneous. The complex compounds may be made by boiling under a reflux condenser highly oxidized logwood extract and water with potassium bichromate, a mixture of copper sulphate and potassium bichromate or ferric chloride. Other examples describe the colouring of (1) a moulding powder of phenolformaldehyde condensation product with the chromium compound of highly oxidized logwood extract; (2) a lacquer from a phenol-formaldehyde condensation product with the chromiumcopper compound of an oxidized logwood extract; (3) a moulding powder of ureaformaldehyde condensation product with the iron compound of a non-oxidized logwood extract; (4) a nitrocellulose lacquer containing tricresyl phosphate and butyl acetate with the nickel compound obtained by metallizing a mixture of 30 parts of logwood extract and 10 parts of Persian berries; (5) a nitrocellulose lacquer with the copper compound of logwood extract.ALSO:In a coloured plastic mass or coloured mass capable of conversion into plastic condition made from natural or artificial waxes, free from oil and containing, if desired, solvents which are not water-soluble alcohols, there is incorporated a complex metal compound of logwood extract. Suitable metals are chromium, copper, iron, cobalt, nickel, aluminium, manganese, zinc, vanadium, titanium, tungsten, or molybdenum. The metal may be used as hydrate or as salt with an inorganic or organic acid, or as a complex compound with ammonia or pyridine, or as a complex metal compound of logwood extract, and the treatment of the logwood extract may be effected in acid, neutral or alkaline medium. Oxycarboxylic acid, e.g. tartaric acid, formic acid, pyridine, or a salt of an inorganic or organic acid may be present during the formation of the metal compound. More than one metal may be used. The base of the plastic mass may be carnauba wax, or ozokerite. The colouring matter may be incorporated by grinding solids together, and may, if desired, be produced in the sheet to be coloured. A fatty acid of high molecular weight, a filler such as barium sulphate, zinc oxide, or titanium oxide, or a softening agent or plasticizer, e.g. tricresyl or triphenyl phosphate, glycerine or castor oil may be added. The complex chromium compound is made by boiling under a reflux condenser 50 parts of highly oxidized logwood extract and 800 parts of water with 15 parts of potassium bichromate in 50 parts of water. 50 parts of common salt are added to bring the compound into filterable form.ALSO:In a coloured plastic mass or coloured mass capable of conversion into plastic condition, free from oil and containing if desired solvents which are not water-soluble alcohols, there is incorporated a complex metal compound of logwood extract. The base of the plastic mass may be copal, amber, shellac, colophony, carnauba wax, ozokerite, casein, rubber, balata, or guttapercha. Suitable metals are chromium, copper, iron, cobalt, nickel, aluminium, manganese, zinc, vanadium, titanium, tungsten, or molybdenum. The metal may be used as hydrate or as salt with an inorganic or organic acid, or as a complex compound with ammonia or pyridine, or as a complex metal compound of logwood extract, and the treatment of the logwood extract may be effected in acid, neutral or alkaline medium. Oxycarboxylic acid e.g. tartaric acid, formic acid, pyridine, or a salt of an inorganic or organic acid may be present during the formation of the metal compound. More than one metal may be used. The colouring matter may be incorporated by grinding solids together, and may, if desired, be produced in the sheet to be coloured. A fatty acid of high molecular weight, a filler such as barium sulphate, zinc oxide, or titanium oxide, or a softening agent or plasticizer e.g. tricresyl or triphenyl phosphate, glycerine or castor oil may be added.