Fill Handles are the squares on the ends of fill arrows. To change the colors in the fill select a handle and apply a color to it. To easily swap between the start and end handles, press TAB (this swaps the selected status of all handles). Note that this only works in the Fill Tool. Fills can be edited using the Selector Tool if fill handles and fill arrows have been enabled in the Selector. See Enabling fill handles and fill arrows. You can change the way redraws are performed during the drag, see Enabling interactive fill and transparency dragging.