Recent work (Kunjwal and Spekkens, Phys. Rev. Lett. 115, 110403 (2015)) has shown how operational noncontextuality inequalities robust to noise can be obtained from Kochen-Specker uncolourable (or KS-uncolourable) hypergraphs without assuming that measurement outcomes are fixed deterministically by the ontic state of the system in an underlying ontological model. This result was obtained by an explicit numerical enumeration of all the extremal points of the polytope of (measurement) noncontextual assignments of probabilities to the KS-uncolourable hypergraph.