Should I change “colour” to “color” when incorporating a Canadian article into an American book?
Changing the spelling of a single word, in multiple places, from British to American English seems odd. Enforcing a particular writing style (e.g., American English) on all authors is fairly common. Ideally, you will have a professional copy editor edit the book. The copy editor will need to be given stylistic guidelines including spelling, word usage, abbreviation, citing, referencing, numbering and many other aspects. Once the chapter has been copy edited, it should be returned to the author for her final approval.