If I'm using the APA Style rules, should I use Canadian or American spelling?
The Publication Manual of the American Psychological Association (American Psychological Association, 2010) is an American publication, so the manual requests that authors use American spelling (p. 96). However, if you're a student at Royal Roads University, you're studying at a Canadian university, so Canadian spelling is usually preferred. You could check with your instructor to see if s/he has a preference, but if not, please be consistent. That is, if you're using Canadian or American spelling, use the same approach throughout the document and don't flip between them.
American Psychological Association. (2010). Publication manual of the American Psychological Association (6th ed.). Washington, DC: Author.