The property FillColor determines the color used for filling the following data items: Bar3D, Rectangle, RectFrame, and Ellipse. In addition, it controls the void color of dashed lines (cf. DrawTo and Line).
The color is stored internally along with the graphics objects so that each graphics object can have a different color. See the Delphi documentation for details on the TColor type.
||Try to avoid situations where the colors of the data items are permanently changed during the drawing process. This will slow down graphics by up to 20 %. Instead, data items of the same color should be drawn, and then the items of the next color and so on.