Abstract: Methods and apparatus for aiding the user of graphics systems to visibly distinguish areas (images) on a display screen generated from raster data from areas on the same screen generated from vector data. An example of where the invention may be applied is in graphical systems in which geographic information is displayed with the graphic data being made up of both vector data (such as a set of points defining a road input to the system by the user via a digitizing tablet) and raster data (such as a photo image of the same road that is digitized via a scanner). The brightness of each data type (vector or raster) image being displayed may be modified by the user. In one embodiment of the invention, in response to user interaction with the system, the brightness of the raster data, the vector data, or both (and hence their images once displayed), may be modified by adjusting entries in color tables (or specific entries of a single color table) maintained for each data type.