@silverwizard N95s are a working surface of the whole and function by grace of a LOT of industrial design. I would avoid customizing one if I needed it to work.
Respirators, well, https://docs.google.com/spreadsheets/d/1NuYVJasqD08cqrROVwoL9COoYtCHrLRYXShg4MtTHe4/edit?gid=0#gid=0
has some material information and you could go from that to paint compatibility.
(My gut-level flinch response is that the fate that finds you for altering safety equipment will be strange to mercy. This is plausibly excessive and as specific consequence of my misspent youth.)