The use, misuse and abuse of the lowly "U" has caused a slight degree of heartburn. A quick search of the mysterious & unsubstantiated internet revealed the following otherwise useless & questionable information.

For most it's common language, for others living most of their life in the US/Canadian border country, except for the 10 memorable years exiled to redrock Utah, the inserted "U" is a familiar and comforting site. For others living north of the 49th parallel........well, they just don't know any better

"Canadian English generally follows British spelling, but often the American alternative is possible too."
1. Australian English also generally follows the British tradition.

British Canadian American
behaviour behaviour behavior
cheque cheque check
clamour clamour clamor
colour colour* color
favour favour favor
favourite favourite favorite
honour honour honor
humour humour humor

Or as Junior Barnes once famously stated in a cucumber field in 1974, "We're all a bunch of cabbage heads on the banana boat of life". Inspirational

"It's not what I say that's important, it's what you hear" Red Auerbach