Sunbaked Interior Window Sills/Shelf, What to do to fix or what paint to paint with?

These are from 1985 and i believe used to be white and are now yellowed. Theyre not all this yellow or all yellow entirely so that's why i believe it's from the sun. Windows face east and west.

I just want to know what i can do to either fix the yellowing, or what i should paint over this surface with that won't chip and will look good.

https://imgur.com/a/rV5hj89