The Flash on Clash in a Ultra Saber is controlled by the Obsidian Sound Board. Ultra Sabers offers quick disconnects (on sabers that are MLS compatible) to be able to swap colors. They offer MLS units with Flash on Clash for an additional cost.
Couldn't have said it better myself.
There is a drop down box for the MLS units that allows you to select the Flash on Clash option if that's what you want.