Abstract: A process for colouring the glass materials to obtain decorated articles of glass-ceramics by the diffusion colouring technique, comprising the steps of: heat treatment of a precursor material or an article made of a transparent glass in vapours of a colourant selected from the group consisting of CuCl, CoCl2, NiCl2, MnCl2, or their mixture, in the following controlled temperature-temporal mode: continuous or step-by-step, with isothermal holdings, heating to T=800-900° C. at rate of 300-500°C./h, and after the final isothermal holding—heating to 950-1150° C. at rate of 300-900° C./h, holding and cooling.