In my experience, by the time you finish scrubbing the part it will already have discolored. If you don't want the discoloring best to use something else.
Engine degreaser won't discolor alumnium but it works best when the parts are warm & it's expensive for what you get in an aerosol can.
Good ol mineral spirits works good too but don't use it on painted surfaces, some plastics & rubbers, etc. Here where I live mineral spirits is banned anyways, not sure about up there. I have to get it out of state.
Not sure what you're dealing with but just warm water & soap may actually work fine for you. Many dish soaps actually work well as a mild degreaser. I would try the dish soap or WD-40 first as you probably already have it. Then look for something stronger if needed. A firm bristle bush & fine scotchbrite used lightly will help a lot too.
