Create a circle on a vector layer
Select the circle
Go to the Stroke and fill docker
Click on the Fill square
Select a solid fill by clicking on the "Solid" button
Even though there is a color on the right, this color does not become the solid color of the object.
(Same behaviour with the gradient)
User has to click on the color in the combo box to assign it to the current shape.

The problem is that the color, or the gradient, on the right are not a representation of the current color/gradient of the selected object. I think this is counter intuitive.