Is it possible to add two floor plans in one virtual tour?

 Answer:

With Tourweaver professional you can edit the color of the skin buttons in the properties panel of the buttons.

Also, there is a way to have more than two floor plans.
First, import the floor plans via the Map tab in the List. Second, add the corresponding control buttons, and then add an action to the buttons that is "Link to Map" to point to the correponding map. That's all. You could see samples here at Galley and download Tourweaver pro to have try