UI - Controls alternate colour states are unused

[LambdaSix]

When a control is being drawn, checks are made to consider the MouseOverHighlight flags and IsActive.

If a control can have a mouse over highlight and is active (has focus) at the time, it will be drawn differently. The problem occurs with controls that add additional drawing layers over the base.

For example, a button draws the button label as the last stage, which has the effect of overwriting the existing colour information. These controls possibly need a special Label pigment with a transparent background colour.