Word's highlight feature lets you mark up your document onscreen just as you would use a highlighter pen to mark up a printed document. Highlighting is designed for use on documents that you'll edit onscreen, but it will also print out. If you don't have a color printer, highlighting prints in a shade of gray.
To use the highlighter, follow these steps:
The Highlight button shows the color that you most recently selected from the palette. If you want to use that color, click the button itself in step 1 instead of choosing a color in the palette.
To remove highlighting, select the text, display the Highlight palette, and choose None.