BrE (en-GB) Support

I use British English. Is it possible to add support for it?

Isn’t that an os-level setting? The Supernotes app itself uses British English and conventions for dates, etc.

Maybe? I don’t know because my Windows language is set to en-GB. Supernotes won’t accept British conventions such as colour.

That’s strange, especially since the Supernotes app interface itself uses British English. As far as typing goes, the app allows British English on my end, and my os is set to American English. (I run the Mac desktop and iOS apps.)