At the bottom of the toolbar there is a box with two lesser boxes and an arrow. The uppermost box displays the present foreground color; the lowermost box shows the present background color. You can single-click on the arrow to switch these two. You can also double-click on either of the color boxes (or one-click if that box is already selected) to pop up a color selection tool, with which you can elect any color you like for that box. That color then becomes the new foreground or background color. Subsequent drawing operations (with text and color fill) will now use these colors.