Re: What type of oil?
Color is the least important part of oil, you need lower unit oil, it is different than 80-90 in that it has additives to deal with water intrusion.
Walmart has it in the fishing section, it is about $4 a quart, you can buy brand name for 3x that but I am convinced it isn't any better, I have run Wally world oil for years with no problems.
Buy 2 quarts, fill one completely to the top and fill your lower, save the other for when you change it again, I do mine 2 times a year, helps keep an eye on what the lower is doing and if you need seals.
Oil $4, lower unit $800, easy math there.
But NO, do not put 2 stroke oil in your lower unit, it will be dead in about an hour if you do.