'65 Barracuda A/C Controls

Those buttons in the 2nd gen' controllers are flat where early/yours have a vertical offset. So what I have here wont help you. That degree of yellow discoloration probably wouldn't back out or bleach out in this lifetime. To remake them, using acrylic resin in silicone molds...
I would have to try if they were mine. Good luck
Redfish,
As it happens a friend of mine who restores old radios has used the same method to reproduce broken /missing radio knobs & luckily another friend has a good set of buttons which we can take a mould of so hopefully there might be light at the end of the buttons yet !