That's not what deguassing cpoild do though
It's nothing to do with CRT's been magnetically deflected (even though they are), it's to do with the shadow mask, a thin sheet of metal full of holes that makes sure each beam only hits the correct coloured spot on the front.
If this sheet gets magnetised, it bends, and this makes the beams hit the wrong colours - because the metal is so thin (and full of holes) even the earths magnetic field causes it, try rotating a TV while it's ON.