Mercury is now selling oil under Mercury, Mercruiser and Quicksilver. Be very careful to make sure you're using the 4 stroke Inboard/STerndrive oil. 25-40 is a weird weight and difficult to find anywhere other than the previously listed Merc. brands. As for Merc filters, we're talking 1-3 dollars per year here.
As for the oil color, how did you 'check' it? Was it by way of the dipstick? The oil isn't circulated through teh dipstick tube. You can drain the oil and look at it, or suck a little out of the dipstick tube with an oil pump (make sure to pull more than the volume conained within the diptstick tube), or you can pull a valve cover and look at it.