That awkward moment when you can’t remember how Americans are supposed to spell a certain word…
Just turn your spellchecker to the UK setting and it’ won’t bother you about using the ones you like any more.
I have this problem frequently. I get my little red, squiggly line under something in Word and think, “But… that’s how you spell that!” Then I go Google the word and discover that I have, in fact, used a British spelling without realizing it.
This is what living across the Pond/reading books published in the UK/Tumblr will do to you.