1.  Field of the Invention
This invention relates generally to a graphics display in a data processing system, and more particularly to the automatic generation of different colors and shades of colors to fill out areas of the display. 
2.  Description of the Prior Art
Graphics and alphanumeric text are displayed visually in many business applications.  This allows the relationship between many variables of the business to be presented in pie chart or bar graph form.  The graphics may also be used to display and manipulate mechanical or electronic designs in color. 
In order to readily differentiate between areas of the graphics display, adjacent areas may be filled using different colors for adjacent areas. 
It has been shown that the use of color displays reduces the operator error rate considerably. 
Prior art systems use a number of techniques for displaying color.  One technique uses multiple memory planes for storage of codes representing different colors and shades.  This approach requires a large amount of memory with its associated control logic. 
A second approach uses an analog display tube whereby varying signal levels represented by coded information stored in multiple planes of memory.  This method requires large amounts of memory plus analog circuitry to drive a more expensive display tube. 
A third approach uses software to mix the colors by having coded information stored in main memory for each desired color.  These codes are used to do paints to bit mapped memories by overlaying different colored patterns to obtain desired colors.  This software approach provides additional overhead for the operating system thereby requiring additional memory and also reducing the throughput of the system.