What does a red light mean on a GFCI outlet?

A solid or blinking red light on your GFCI outlet means there's a problem with it. Your GFCI performs regular self-tests to make sure its working properly. If your GFCI fails the self-test, the red light will turn on. All you need to do is press TEST and RESET to reset your GFCI. If it fails to reset, you'll want to replace it right away.