Export OBJ files with vertex colors in blender.
Importing is currently unsupported.
(r,g,b values are added to the end of each vertex (like meshlab) in the .obj file if you need an importer)
Works only with Blender 2.79 (probably).
Go to your blender installation folder and put it in the addons_contrib folder
(Program Files > Blender Foundation > Blender > 2.79 > Scripts > addons_contrib)
Enable it in your user preferences. It might be categorized under 'Testing'
OBJ export taken from blender 2.79