Oh, I see! Thank you for pointing out the episode. So it would be a custom "Custom K.I.T.T." K.I.T.T. kit!
The grey one is the acid-eaten K.I.T.T. from "Junk Yard Dog":
Knight Rider (1982) 3x14 Junk Yard Dog - ShareTV
K.I.T.T. appeared in a white paint scheme there, too.