Applying a Glow effect adds a nice halo around a selected shape or most other slide objects. You may find that the Glow effect defaults do not work for you all the time, especially since the default glow options are limited only to Theme Colors. So if you want to make some changes, you have to step outside these defaults and change the glow color, alter the spread or transparency, etc.
To learn more, choose your version of PowerPoint. If we do not have a tutorial for your version of PowerPoint, explore the version closest to the one you use.
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