I've not had that happen.Why not try a mr clean eraser to a spot that it not so easy to see and see how that works.I use one on my tea cups as they stain so bad.Just be sure to follow up with a soft wet (not dripping) cloth.
Worth a try don'tcha think.
Kathi
PS let us know how it goes.

Try googling "how to clean yellowed computers". I would think the plastic components would be similar.

Ignore it. You risk making it brittle as well as discolored.

Or spray paint it with something meant for plastic.

Thank you so much for the advice! First thing I did was clean it with bleach and water -- a little bit of bleach and a LOT of water. That helped it immensely, just getting it clean.

I tried a Magic Eraser. While that helped to get a smudge off of some sort, it didn't help the whole picture. Of course, my Magic Eraser might be worn out.

Doing a search about cleaning yellowed computers, it suggested a product that is mostly hydrogen peroxide. We don't happen to have any in the house, so will pick some up on my next trip out, and give that a try.

In the meantime, the machine sews beautifully, so I may just have to live with the aging plastic.

Donna