A gradient fill is a colour that fades or darkens from one side to the other. You can have just one colour that fades to a lighter shade or you can have two or more colours that blend and change shades. From the Format Background dialog box, click the down arrow to access Fill Effects. PowerPoint does not display the gradient fills for you, but the dialog box does give you the tools to create your own gradient fill. As well, your effects can be previewed from the Fill dialog box.