Intimidate is an evasion ability defined in CR 702.13. Specifically, CR 702.13b states that a creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it. This means a blocker must meet at least one of those two criteria to legally block.
So the answer is: a blocker is legal if it is (1) an artifact creature, OR (2) a creature that shares at least one color with the attacking creature, OR (3) both. It is not restricted to only artifact creatures, nor does it require a blocker to be both an artifact and the same color.
Color sharing is checked against the attacking creature's actual colors (as determined by its color indicator, characteristic-defining ability, or mana cost). A colorless creature with intimidate, for example, could only be blocked by artifact creatures, since no creature can share a color with a colorless creature.
Concrete example: Your opponent attacks with a Red intimidate creature (say, a red 2/2 with intimidate). Your opponent's blockers are: a green artifact creature, a blue non-artifact creature, and a red non-artifact creature. The green artifact creature can block (it's an artifact). The blue non-artifact creature cannot block (not an artifact, shares no color). The red non-artifact creature can block (shares red with the attacker).
In summary, intimidate requires a blocker to satisfy at least one of two conditions — being an artifact creature or sharing a color — not necessarily both at once.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.