On the US lights the fogs are a white bulb with a yellow (cadmium) cup that snaps on. There is no mount to attach the cap to Euro lights as I understand. You could try to locate a set of cadmium coated H-3 fog lamps (good luck) to keep the yellow light with the Euros.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.