On plastics and aging
Yes indeed, certain chemicals can react, alter, or interfere with the light emitting properties of the plastic, thereby altering the color.
One of the most common ways to cause this however is with exposure to UV light. Many kitchens, laundry rooms, and garages have flourescent lighting in them, especially in constructions since the 1980s, and exposure to the UV degrading elements of this type of light will quickly yellow certian light colored plastics. If a material is exposed to heat, humidity, or surface-tension altering chemicals (surfactants) this can accelerate the yellowing.
We see yellowing all the time on certain products, especially dishwashers with plastic control panels, when their color was originally white. These turn an ugly yellowish beige. Same is true for end caps and some knobs on WP-made DD washers, GE plastic knobs on white panel washers and dryers, etc.
I am not sure its completely possible to remove this yellowing or color alteration. It depends how deep into the product that the molecules have been effected. This is not unlike the yellowing on automotive headlamps. There are treatments (such as buffing compounds and rubbing compounds) which remove the damaged layers of material and reveal a proper colored, "new" surface. If not protected from UV exposure in some manner, these surfaces will become altered again. On the other hand, if the material has yellowed all the way through, or effectively aged permanently, it may not be possible to bring back the original appearance.
Keep in mind also that the properties of some thermoplastics, especially vintage ones, can not tolerate exposure to strong chemicals, and can partially dissolve, break, or crumble.
The only way to guard against this is to use better pigments in the coloring process during molding. This however ads cost, so some manufacturers do it for color stability (there are also UV stabilizers which improve exposure tolerance to sun) other don't, it depends on budgets.
Gordon