Reduction

Not too bad.

• Triangle: true, false, red.
• Each literal becomes a node with an edge to ``red.'' Its color (which can only be ``true'' or ``false'') represents its assignment. A literal and its complement are connected by an edge to assure that they don't get the same color.
• Each clause becomes a set of 5 nodes: insures that all 3 literals are not ``false.''

Graph has a 3 coloring if and only if formula has a satisfying assignment.