I need to contaminate margarine with a fairly large dose of cod liver oil without significantly altering its appearance. Any ideas?

Ioana: Melt it, mix it, pour it back in the tub, let it cool off

Me: Doesn't it separate? I mean when you melt it.

Ioana: I don't think so. You don't have to bring it to the boiling point, just melt it.

Me: Eeeeexcellent.

Ioana: Hope it works!

Me: Knowing me, I'm just gonna do something grown-up and responsible like get a lock box to keep the roommate out of my food. But if I go with the cod liver oil, I'll let you know how it goes.