For those TSers on the other side of the pond, you can post your humour also. In the US, it's "humor." In the UK, it's "humour".
Winston Churchill is supposed to have said that America and Britain are two countries separated by a common language. Certainly that's true of spelling. Among other peculiar (to the American eye!) British spellings are "honour" and "favourite."
While British pronunciation differs from American, I don't believe that the British pronounce these words in a way that would reflect the spelling difference: "humour" isn't pronounced "hum-u-or" or "hum-o-ur."