i've been experimenting with that a bit in the past and (thought, depending on the setting you use is very heavy for the engine to deal with) it is possible to work on light colours, opacity as well as size and other stuff, works with both day(night animations and animloops so its just a matter of testing and dealing with the cpu overload (though with simple on/off switch, which should be set from the colour box (black/whatever colour you want) there is no overload)