Creatures you control gain intimidate until end of turn. (Each of those creatures can't be blocked except by artifact creatures and/or creatures that share a color with it.)
A multicolored creature with intimidate can be blocked by any creature that shares a color with it, in addition to artifact creatures. For example, a white-blue creature with intimidate can be blocked by white creatures and/or blue creatures, no matter what other colors they are.
If an attacking creature has intimidate, what colors it is matters only as the defending player declares blockers. Once it’s blocked, changing its colors won’t change that.