Reminds me of the Lingthusiasm episode where the Canadian and the Australian hosts discuss a book about the differences between British and American English. Both fell somewhere in between

Often, specifically the word colour

I strongly suspect that whatever spellchecker you’re using has the option to have a user dictionary of added words that you want it to accept.

EDIT: If you mean Fedora Linux, I don’t know what program you’re talking about.

I’d guess that it’s either aspell or hunspell.

Hunspell doesn’t seem to have a Canadian English Fedora package:

https://packages.fedoraproject.org/pkgs/hunspell-en/

Looking at the package file list, it looks like the files required for US English go in:

/usr/share/hunspell/en_US.aff

And:

/usr/share/hunspell/en_US.dic

But it does look like a Canadian English dictionary exists:

https://github.com/wooorm/dictionaries/tree/main/dictionaries/en-CA

I see an index.aff and index.dic there.

I don’t know why Fedora wouldn’t have a Canadian English hunspell dictionary package. Debian does:

https://packages.debian.org/sid/hunspell-en-ca

And Aspell does have Canadian English:

https://packages.fedoraproject.org/pkgs/aspell-en/aspell-en/

Provides the word list/dictionaries for the following: English, Canadian English, British English