You can fill any element or page with colors that blend into each other, called color gradients.
Use the format bar to quickly add a color gradient to an element. Select the element, click the Fill well, and then choose a gradient from the gradient matrix or click Show Gradients to open the Gradients window for more choices.
You can also use the Graphic inspector to fill an element with color gradient.
To learn more about using the Gradients window, see The Gradients Window.