Computing Ribbon Obstructions For Colored Knots

Kjuchukova's Xi(p) invariant gives a ribbon obstruction for Fox p-colored knots. The invariant is derived from dihedral branched covers of 4-manifolds, and can be used to calculate the signatures of these covers when singularities on the branching sets are present. In this note, we give an algorithm for evaluating Xi(p) from a colored knot diagram, and compute a couple of examples.