ambiguous color setup for a single tetrahedron

[Bin Wang]

For a single tet, #f = #v = 4, how can I set up vertex color for a single tetrahedron?

The color setup rule is not valid for a single tet:

The key parameter c represents the vertex or face colors and can be one of the following:
A #v by 1 vector with one function value per vertex, which gets normalized and converted into vertex color values using the viridis colormap.
A #v by 3 vector with RGB color values per vertex. The color values should be in the range 0.0-1.0.
A single color value for all vertices in the form of a numpy array [R, G, B] in the range 0.0-1.0.
A #f by 1 vector with one function value per face, which gets normalized and converted into face color values using the viridis colormap.
A #f by 3 vector with RGB color values per face. The color values should be in the range 0.0-1.0.