Coating composition comprising a char forming compound as a first compound capable of forming a colored substance upon exposition to energy; at least one latent activator selected from the group consisting of ammonium phosphate, ammonium polyphosphate, ammonium sulfite, ammonium thiosulfate, ammonium sulfamate and ammonium sulfate; and a second compound capable of forming a colored substance upon exposition to energy selected from the group consisting of color formers, oxygen containing transition metal compounds, and metal-chelate-type color forming systems; a coating composition comprising a char forming compound as a first compound capable of forming a colored substance upon exposition to energy, and a second compound capable of forming a colored substance upon exposition to energy selected from the group consisting of color formers and metal-chelate-type color forming systems; a process for the preparation of these compositions, substrates coated with these compositions and a process for their preparation, a process for preparing marked substrates using these compositions and marked substrates obtainable by the latter process.