Other threads have mentioned stuff like acid-etching primer in order to paint stainless steel. Certainly it is possible.
Personally though, I have to agree with Krash. There's going to be some bonkers wraps done on this. I'd quite like to see Dazzle Camo from the WW1 ships.
How Tesla's Cybertruck Turns Car Engineering Norms Upside-Down - Motor Trend
Per this article................No paint.
No paint required, not no color available.
Steel can be made in several colors
Electrochemical and chemical finishes of stainless steel | Gasparini Industries shows you what colored steel looks like.
I'd assume there will be multiple color options from the factory when these things go into production.