The original spelling of the word now commonly spelt as color. Colour is the outdated version that people rejected partly because its pronunciation didn't match the way it looked. The use of a 'u' in the word was understood but it was removed because intelligent folk realised it was completely unnecessary.
What's more, if a company needs to have several signs made that additional u will increase the total production cost. American know this because they are more business savy.
Typing a long screen play or book with extra us in everything just means you'll get carpal tunnel faster. Those Us add up after all ya know; save time. Make sense. Drop that u in colour!
The British way of spelling color. Americansspell it "color" which is the better way to spell it. It's shorter and easier.
American dude: Why the hell did u spell color with an extra u?
British dude: because spelling colour without the u is absolutely absurd and---
American dude: you've gotta be shittin me!
British dude: its unproper to use colour without---
American dude: Just shut up. No one gives a fuck.