Water based paint and just regularly checking the tyre wall immediately under the paint.
To do this I suggest some sacraficial test paint spots on the inside of the tyre, mirroring where you are planning to paint on the outside walls. These you can paint and then clean off/rub down and check the underlying rubber. Would do this for a year thus covering all temeprature/environment changes before painting large areas.
There is a good 2mm to 5mm of rubber on the walls of a tyre before the inner structure and rayon/fabric inner structure. I doubt a water based paint will ever penetrate this wall thickness (assumption here is a tyre less that 5 years old) BUT it is YOUR DUTY and RESPONSIBILITY check for yourself.
Disclaimer! I've only ever used proper tyrewall paint, and that was a long time ago in the past.
If you want to be absolutely safe, legal, etc. then PLEASE only used certified tyrewall products.