There is provided a method of changing a theme for a user interface of a computer system comprising receiving an identification of an image with which to define a color palette of a theme for rendering elements of a user interface on a color display of the computer system; analysing the image to determine at least one predominant color; and defining the color palette in response to the analysis. The image may comprise a background image selected by a user for display by the computer system. Dynamic generation of the color palette matches the user interface to colors to provide flexible and appealing themes. A computer readable memory having recorded thereon instructions to carry out this method is also provided, as well as a device comprising such memory.