1. A method for processing a digital video stream of colour images intended to be displayed on a matrix screen formed of macropixels having at least four subpixels each, each of the images comprising three colour components in a first RGB format, the method comprising: a transformation of the colour components of each image into a second RGB format based on a polygonal representation of the colour components and designed for the display of images using at least four colours by activating the four subpixels, wherein said method being characterized in that the colour components of the image are adapted in the course of said transformation.