Sets the color for the region bounded by the rows START-Y and Y and the columns START-X and X (inclusive). When you set REGION-COLOR, any previous region color is removed and a new region is set. The boundaries of the region are set when REGION-COLOR is set. Subsequent changes to X, START-X, Y or START-Y have no effect on the region until the next time that REGION-COLOR is set.
Region color is normally used to highlight an area being marked by the user while dragging the mouse. To do this, usually all you need to do is set REGION-COLOR to the desired color in response to a MSG-GOTO-CELL-DRAG event. Note that when this event is generated, START-X, X, START-Y, and Y all have sensible values in them, and they usually do not need to be set by your program.