So, that is not a bug.
But, the "fix" is to create a white colour material and assign it to the object we want to use the vertex colour (note that we must to keep the Vertex Color property in Material's dialog defined as Set).
But, the "fix" is to create a white colour material and assign it to the object we want to use the vertex colour (note that we must to keep the Vertex Color property in Material's dialog defined as Set).