Paul,
I also found it odd that return oil was somewhat creamier looking that the rest, however, I believe that is because the bubbles in the oil lighten the apparent color of the oil. Additionally, if you used white assembly lube when putting the engine together, that might make the initial circulation lighter in color. While I don't think the creamy appearnce is a problem, it can be a good idea to idea to drain oil after intial startup, just to see if there is anything bad floating around.
Richard