I recently picked up a Tandy 1000HX with severe key discoloration, and after perusing my options, went with some peroxide hair care product.

I popped all the keycaps off, tossed them in a large ziploc bag, and dumped a half-cup of the goo in. I left them in the sun for a couple of hours, and I'm pretty pleased with the result.

HOWEVER, you may notice a slight problem in the "after" photo... I have no idea where my "D" keycap is. I've looked everywhere!

Digging through the rest of the trash tomorrow, looking for the old bag of hair treatment, I am hoping I just left it in the mess of goo...