Twin F200 gear box oil colour difference

[Simon E]

photoportstabgearboxoilf200.jpgI recently changed the oil in both gear boxes and the starboard side is a lot darker than the port .I have included a photo any suggestions ?

[rodbolt17]

typically its the port,or left hand case, that comes out darker.
years ago I asked that question, and there is a tech bulliten on it about the left hand case oil color.
what they said and the tech bulliten said, is its the molybedenum assy grease used on the left hand case.
I go more by smell of the oil than color.
not the first time I ever saw the left hand rotation case on the stbd side either.