I would like to suggest that we uses Canadian English spelling for the wiki. As the game is set in Canada and developed by a Canadian studio, it seems logical that we use it on this wiki.
Canadian English is normally closest to US spelling, but some words are the same as British English.
It doesn't have to be strict rule, but rather a guide, so that if there is any dispute about a spelling, we will use the spelling that is most common in Canadian English.
This website has some good tips on standard Canadian English spelling, as well as a searchable database of some words.