I had whitewalls on my 1980 MGBGT. At that time it had become the fashion, and dealers had the whitewalling machines - of which there must be some still around. I wouldn't have gone for this option, but it had already been done. A thin layer of white material was laid in an abraded ultra shallow groove in the sidewall.
What happened was that the oils in the rubber yellowed the white very quickly. In the end I used a whitewall crayon to stop them looking tatty, but the flexing of the sidewalls meant that the surface was always cracked in appearance. I suspect that the same process will take place with the orange walls.
