As you've worked with effects and motion settings, you may have noticed a few more colors popping up in the timeline. Here's a rundown:
A green line at the top of the Audio or Video portion of a clip indicates an audio or video effect has been applied to it.
A red line at the bottom of a clip indicates motion settings have been applied to it.
A red line directly below the work area bar indicates clips with video effects, motion, or transitions that need rendering before export.