Yellow headlights allowed?

French cars had yellow headlights until the beginning of the 80s (in France ). I always assumed that yellow headlights were forbidden in Germany, so that one had to convert to white in order to get a German registration. Today, however, I saw a Peugeot 504 with German approval, which had yellow headlights, and a total of 4 additional headlights. Two of them were also yellow and two white. Are yellow headlights allowed after all?