You can
open the Preferences window by choosing Preferences from the
menu or
by clicking the Preferences icon in the Main
Window. You can change the following settings in this window:

Start Interruption When Screensaver starts · If you turn this on, Time Tagger will start an Interruption when your screensaver turns on. This is a great way to avoid running a meter when you are called away from your computer. When you return to your computer and de-activate the screensaver, Time Tagger will pop to the front so you can tag your interruption slice.
Turn off All Tags When Sleeping · Turns off tags when your computer goes to sleep.
Tag Text Size · Control how big the tags appear.
Tag Colors · Choose your preferred colors for the on and off states.
Error Window Settings · Control how Time Tagger reports errors and warnings.