There are a few ways to print white on a computer printer but it takes special bits to do it.

1. Using a LONG out of production ALPS printer and the corresponding white cartridge.

2. Using a special white toner (VERY EXPENSIVE!) with a compatible printer. Think about 350 or more GBP for the toner cartridge. Here is a link:
https://www.ghost-white-toner.com/

3. There is (was?) a company on the continent(Don't ask me the name!) that has a special paper that you can print white on. The white transfer will NOT allow you to overspray with any kind of clear coat or the white ink (or whatever it is)is lost. There is also a company in the USA that sells a similar (if not the same product) called Hobbycal.

I make no recommendations or make any endorsements as I have not used ANY of these products (yet). In the long run its not really worth it unless you plan to do lots of white decals.

I hope you found this of interest.
DonH