Extrude silicone from caulk gun into a bath of soapy water.
Extrude the silicone into a container, add tint to silicone and mix, then scoop into empty caulk tube and close, then extrude the same as steps above. Extruded filament will have small air bubbles that cannot be removed (unless a pessure chamber is used), but these bubbles give a sparkly effect to the filament, however it does weaken the overall filament