Well, that specifically, can’t happen. The traffic lights have what is called a “Malfunction Management Unit” - which is hard wired to look for “incompatible” light combinations, such as all being green.
https://jhalderm.com/pub/papers/traffic-woot14.pdf
Intentional tripping of the MMU can often result (depending on manufacture/configuration) flashing yellow. All flashing yellows would be just as bad.