[data_hope]

Funnily enough, there is precedent, that a red light can be ignored if it doesn't change for 5 minutes. And I really doubt that there isn't a way to regulate the crossing without a permanent red light.

http://www.stvo.de/info/faq/165-ampel-bleibt-rot (German)

[mmarx]

That allows you to assume that the traffic light is defective, in which case the traffic signs would apply and require you to turn right—but that is exactly what is allowed by the green arrow even at a red light.

[data_hope]

ah you are right, probably there is a blue right-turn only sign (I just thought about the Grünpfeil depicted in the illustration image).