PBT doesn't yellow, at all.
Dye-sublimated legends can slightly fade from extended UV exposure. But that's just black legends turning dark grey...
PBT doesn't get yellow.Show Image(http://d2ydh70d4b5xgv.cloudfront.net/images/1/5/vintage-apple-macintosh-extended-keyboard-ii-m3501-tested-guaranteed-0ec5b186a6061f584ae88580657c5946.jpg)
Guess which keys are PBT and which KEY is ABS.
Hurry up, some extras available here:
https://geekhack.org/index.php?topic=78563.0 (https://geekhack.org/index.php?topic=78563.0)
Originative also has some for sale https://www.originativeco.com/products/modern-beige . On the Originative front page there are some codes that give you 10 % off a 100 dollar order!