What Can Cause Invisalign Clear Aligners to Turn Yellow?

One of the selling points of Invisalign clear aligners is that they are made out of transparent plastic, which makes them far less noticeable than traditional brackets and wires. However, in some cases, your aligners may start to turn yellow, causing them to attract the wrong kind of attention. Why do Invisalign clear aligners sometimes become discolored? And what can you do to prevent it from happening?