A call to the global viz.setTheme function after this call will overwrite this call.
darkTheme = viz.Theme()
darkTheme.borderColor = (0.1,0.1,0.1,1)
darkTheme.backColor = (0.4,0.4,0.4,1)
darkTheme.lightBackColor = (0.6,0.6,0.6,1)
darkTheme.darkBackColor = (0.2,0.2,0.2,1)
darkTheme.highBackColor = (0.2,0.2,0.2,1)
list = viz.addButtonLabel('DARK')
list.setTheme(darkTheme)
list.setPosition(.5,.5)
list.setLength(1.0)
list2 = viz.addButtonLabel('REGULAR')
list2.setPosition(.5,.54)
list2.setLength(1.0)