My 7th grade (12 yrs old) English teacher (USA) marked my grades
  down because I started using British spelling. She'd write on
  the papers, "You're an American! Write American!" I had a slight
  obsession (have) with Doctor Who and English stuff generally and
  at the time, I was expressing it. So I would've written
  honoured. I loved writing colour. I still do it sometimes.