1. A method of changing a theme of a user interface of a computer system comprising the steps of: receiving user input via the computer system identifying a color image to display as a component of the user interface, said color image for defining a color palette of the theme for rendering elements of the user interface on a color display of the computer system; analysing the image using the computer system to determine at least one predominant color; defining the color palette using the computer system in response to the step of analysing, using a one of the at least one predominate color to select one or more matching colors or one or more contrasting colors automatically with which to define the color palette; and rendering elements of the user interface on the color display in accordance with the color palette, the elements comprising one or more of icons, cursors, object borders and shadowing, menus, lists, text boxes, input boxes, push buttons, radio buttons, scrollbars and toolbars thereby to color coordinate the elements to the color image.