WIP: Reactive Visual tests and integration of Color with visuals

On a second thought, I will integrate Visuals with Color and then add the tests so that the changes can be included in few commits.
Shouldn't color.rgba return ```None``` instead of ```(0., 0., 0., 0.)```? In case of ```border_color``` attribute, if its ```None``` it means no border will be drawn while ```(0., 0., 0., 0.)``` will result in a black border being drawn.