I find the kwarg colorpoints confusing. Reading through code and seeing tripcolor(x, y, t, C, colorpoints=False) wouldn't indicate to me a solid shading of each face. I think a clearer interface would be tripcolor(x, y, t, facecolors=C).

If you want to allow it to be short circuited to tripcolor(x, y, t, C) depending, of course, on the size of C... well that seems reasonable too.

This looks like a nice improvement. In addition to my commented about faceted, this should have an example and a unit test.

Apologies for taking so long, but I have now addressed the comments. The changes are, in order of my commits:

1. Deprecated shading='faceted' and supported the edgecolors kwarg instead, as in pcolormesh.
2. Removed the confusing colorpoints kwarg and used facecolors instead. I've kept the short-circuited option of not using facecolors if it is clear from the length of C whether it applies to faces or points.
3. Modified the existing tripcolor example to include a facecolors plot.
4. Added an image comparison unit test.

Note that the edgecolors kwarg isn't supported for shading='gouraud'. It would be nice to support this, but I cannot see how without changing many files in the backend code. The behaviour is at least consistent with pcolormesh. I've noticed that pcolor doesn't support gouraud shading at all - I presume the conclusion here is that support for gouraud shading is patchy and needs to be reconsidered sometime.

Thanks very much for the changes.
The merge button is grey, however, so it looks like you need to rebase against master.

I've rebased against master as requested.