4 Coloring Prolog. It will also use unit clauses. Color 4 red x. Color 1 orange y. Color 4 pink y. Color 3 purple y.

Color 3 purple x. Color 1 orange y. Color 1 orange x. Color 4 red x. Color 2 pink x.
Color 4 pink y.
One could declare colorings for the regions in Prolog also using unit clauses. Color 3 purple x. So far my program. Color 5 pink x. Color 3 purple y. In prolog one could declare coloring for the regions. One could declare colorings for the regions in Prolog also using unit clauses. It will also use unit clauses.