Slot Color view
The slot color view provides a color chooser for the currently selected slots.
This can be more convenient than using the slot color button because slot colors can be adjusted without opening and closing a dialog. Also, when an attachment is selected the slot color view sets the color for the attachment's slot. This saves needing to select the slot.
The contents of the slot color view adapts to the view's size. When sized larger, the hue, saturation, brightness, red, green, blue, and alpha controls are visible. When sized smaller, the controls are hidden.
