I've read a few things on here, probably similar to my situation, but still throwing this out there: Both tail lights are out. Replaced bulbs, no dice. Checked the fuse, looked ok, replaced it anyway. Noticed that the license plate lights are working. Also, now, every now and then, I start the car, and the radio is powered off (radio was on when car last turned off), and the Multi Function Display has changed from Orange to Green. Any thoughts? 12V battery? Relay? Thank you. Edit to add: 2007 Prius, about 140k miles, I tried the 12V battery health check and the results seemed "normal" (not sure I did it right?)
How old is the 12v battery, has it ever been changed? If it's the original battery, then it sounds like it's dying and will strand you soon.
On the tail lights, if the license plate lights and side indicators are working that means the switch, fuse, and relay are okay. About the only thing common to the two tail lights is a ground point. Check the continuity to ground from the lamp sockets and fix that if needed. My wiring diagram says the ground is "lower back panel center." Has there ever been a minor rear-end collision? If 12V battery voltage is okay, I'd guess your MFD is going bad. Get the part number off the car and start shopping around for a replacement. There might be a salvage deal on eBay.