Jabalí colmillo afilado

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.

Intimidate looks at the current colors of a creature that has it. Normally, Bladetusk Boar can't be blocked except by artifact creatures and/or red creatures. If it's turned blue, then it can't be blocked except by artifact creatures and/or blue creatures.