Noob roulette question.

[Brom]

Is there any order or reason to the way that roulette numbers are coloured? I always assumed it went something like odds are red and evens are black. Then I actually walked by a roulette wheel long enough to watch what was going on. The red and black squares appeared to me to be randomly thrown down on the board. Any secret pattern, or for that matter, are they the same everywhere?