When you complete a task or when it becomes overdue (oh, yes, those New Year's resolutions), Outlook changes the color of the text for the completed tasks to gray and overdue tasks to red, which makes it easy for you to tell at a glance which tasks are done and which tasks loom ahead, undone. If you don't like that color scheme, however, you can change it by following these steps:

Choose Tools, Options (or press Alt, T, O).

The Options dialog box appears.
Click the Task Options button (Alt, T).

The Task Options dialog box appears.
Click the scroll-down triangle at the right end of the Overdue Tasks box (Alt, O) or the Completed Tasks box (Alt, C).

A list of colors drops down.
Choose a new color for overdue tasks -- or completed tasks.

Green is so much less strident than red, don't you think?
Click OK.