(v2.2.2 Later) Object colors displays dull color.

[micheus]

I don't like that either.

Two years ago dgud said in this post: "Vertex colors are multiplied with material colors, so that is expected."

Which explain this behaviour, but as we keep the Vertex Color option in Material dialog set to Ignore I think we should really expected it to not influence the material color - and vice versa - at least when we are talking about the default material.

Because of that, if you set your default material to White you probably will see the colours correctly.