# Is there a “well known” example of a constraint satisfaction problem on a 3-element set which is polynomial-time solvable?

I'm basically looking for an example (in maybe graph theory) of a constraint satisfaction problem which has a 3-element set as a domain and the problem is known to be polynomial-time solvable.

A more interesting example is linear algebra over the three-element field: The domain is the set of congruence classes $$\bmod 3$$ and the constraint relations are given by linear equations.