A method of colour laser marking an article having a polymeric foil with at least one colourless layer containing an infrared absorber, a polymeric binder and a colour forming compound; including the steps of:—laser marking the colourless layer with an infrared laser using a first laser operation mode to generate a blue or cyan colour; and—laser marking the same colourless layer with an infrared laser using a second laser operation mode to generate a black colour, wherein the first laser operation mode applies less energy to the colourless layer than the second laser operation mode. Also disclosed is an article, such as a security document, including a polymeric foil and a colourless layer containing laser marked graphical data having a blue or cyan colour and laser marked information having a black colour