All The Tropes:American and Commonwealth Spellings

This wiki is used in both America and The Commonwealth. This would be titled "American and British English spelling differences", but the Australians complained, just like New Zealanders complained about All Black Article.

On All The Tropes, here's the guidelines:

1. Use whichever one you're comfortable with.
2. First come, first served. Don't change the spelling in someone else's writing; this will just lead to edit warring.
3. If there's strong national ties to the page in question, it's okay to standardi(s/z)e to one spelling. For instance, it's okay to change "colour" to "color" on Eagle Land, and it's okay to change "program" to "programme" on British Brevity. The same goes for work pages.
4. Create redirects for titles with multiple accepted spellings. This makes the page searchable for both styles. Mixing styles in a title doesn't usually make much sense, though.

For comparison, here's the policy towards this on The Other Wiki.