Agree with Bmoeller, Rotella in mine turns black. Only oil I ever knew of that had a green tint before or after use, was Kendall. For a long time, there base stock came from the area of the Appalachian Mountains. I ran Kendall in all my street rods and offshore boats and NEVER had a oil related breakdown. Mercury Marine for the longest time recomended Kendall GT-40 straight 40w oil in ALL their motors. From the smallest 4 cyl. up to their 572 ci, 1000 H. P. race motors.
Now Kendall is owned by someone else and does not use the same base stock. Their oil is simply brown now... ... ... ...
Jim