It depends on the material. The material defines the color of the object in the presence of lighting. There are two kinds of material definitions: (a) the material says “let the vertex color be seen”, or (b) the material says “the color will be (r, g, b, a)”.
Since both setColor() and setColorScale() affect the vertex color, then if your material is of type (b) then neither of these operations will have a visible effect.
David