For example, here’s a simple chart using the theme called Office:
Here’s that same chart using the theme called Perspective:
As you can see, the theme affects the font, color, shading, and shadow effects. And because it’s available in Word, PowerPoint, and Excel, your chart will look the same no matter what program it appears in – and all the other charts you use will have a similar look.
The Themes gallery is accessible from the Formatting Palette. To create your own custom theme, you can open up a given theme and then alter the font, colors, and effects, and then save as a new theme. Just use the customization settings to the right of the thumbnailed themes, visible in the screen shot below.