1. A method of customizing a customizable theme of a user interface of a computer system, the method comprising the steps of: receiving a base theme comprising a plurality of layers, each of said layers comprising at least one object, at least some of said at least one object having one or more graphical properties; mapping each of a plurality of screens for the user interface to each of said layers, each of said screens having at least one screen attribute associated therewith; mapping each respective screen attribute to the graphical properties related to the respective screen attribute, said mapped screens and screen attributes defining the customizable theme of the user interface; receiving a user input to modify said at least one screen attribute corresponding to a first screen to customize the customizable theme; modifying the graphical properties related to the modified screen attribute; and wherein the step of modifying comprises determining the mapped layer for the first screen and determining the mapping of said modified screen attribute to the graphical properties of said at least one object.