Discoloration

When i buy train either broken or in a lot, there is always that one or more that is sunfaded. (specially the face)
and i have tried different methods of trying to make them look better, but only ends up worse
i have good examples of trains and veichles that are not so great.

these are not in the worst condition, i have worse.

the point with this thread is, How can you remove the discoloration from the locomotives?
because i have tried nearly anything, but the only things that happens is the eye brows dissapearing.
are in middle of moving house so, most of my other trains are packed away. (The engines who are more sunfaded)
Blueberry'S'

[Super]

If the plastic is discolored from the ultraviolet rays of the sun then I am afraid there is no solution, at least I have never heard of one.. This can affect colored plastic as well but white plastic is most affected by the UV rays.

[Ucwepn]

The only way to protect them from fading is to store them away from sunlight, if they are yellowing then that is the bromine in the plastic leeching out to the surface (it's a fire retardant in plastic). can soak the affected parts in 6% peroxide but it will destroy stickers and can wreck tampographs like stripes and eyebrows etc but it does work slowly. Hopefully one day we can buy repro stickers like we can for other vintage toys.