Assertion: tetrahedron's face | /r/HasProperty | same color
Facets:
Source sentences:
text: A $120^o$ rotation about an axis through a vertex $v$: for the coloring to be invariant under this rotation, the three faces adjacent to $v$ have to be the same color; in other words the faces are partitioned into $2$ "orbits", one orbit consisting of the three faces adjacent to $v$, the other orbit containing the remaining face.