You know, oats do spoil more quickly after harvest than most grains, which was one of points against them before they became popular. Because oats are almost always processed in some way before being cut, milled or rolled, they rarely spoil later, and most of us have kept even an open package around for a very long time. I suspect early spoilage, perhaps a pocket of damp grains, that wasn't caught and that probably shows up as color, any odor having been suppressed in processing. Probably happens more than we know, but rolled oats present an opportunity to see the whole grain in one piece reach the table.
It has been claimed that in industrial farming, drying of oats often gets delayed, resulting in a darker rolled oat product, color changes taking place from early spoilage on account of moisture and oil, and that oats should properly be more nearly white.
My own favorite oats have become what Bob's Red Mill claims is original "Scottish oats," stone milled roasted whole oats. More gruel-like than oat bran or rolled oats. Quicker cooking than steel cut.