Set DefaultDrawing to true to have the grid automatically paint the cells in the grid, including adding the background color, the 3-D effects on the fixed cells, and the focus rectangle around the selected cell. Set DefaultDrawing to false to skip the painting of the cells when the grid is drawn. 

When DefaultDrawing is false, the cells should be painted using the DrawCell method. For TCustomGrid, DrawCell is an abstract method. Descendants of TCustomGrid use DrawCell to provide their own customized drawing code, or to generate an OnDrawCell event. 

DrawCell 

OnDrawCell