Blender 2.81 doesn't seem to be importing vertex color for .ply So people have had similar problems showing colors on .ply files here and here  but I don't think this is the same case.  I've exported a .ply file from a program called paraview with color info on it.  I've uploaded the file here and as you can see, the color info came with it.

But for whatever reason when I import it into blender and go look for the per-vertex color info where I would expect to find it, its empty:


Am I doing something wrong?  It seems like there had been a problem with importing .ply color for a bit in 2.80, but this is 2.81.  I would assume it was fixed?
Blender's ply importer only adds vertex colors when they are part of a face or triangle strip. You can see this in the source code of import_ply.py. 

mesh_colors is the list that collects the vertex colors. The assignment of values to mesh_colors and the indices to mesh_faces happens in the add_face() function. This function is only called when a b'face' or b'tristrips' is encountered in the ply object. Only when mesh_faces is not empty and the required color channels are present the new set of vertex colors is created through mesh.vertex_colors.new(). Therefore vertex colors are only imported if the colored vertices were part of a face.