oh,
you can do that easily in a Brain, Use a Timer Pulsing function, set the pulse duration to what ever you want, and put your initiating object for that light purpose. and then terminate to the Local modbus address that goes to that DO. it will flash at the pulse time that you put given that the condition that inititates it stays true.
If you have several lights, i.e. a Red, Yellow and Green for instance you can put your input Initation conditions going to an AND box, and use NO/NC (not inverted, and inverted) to give the conditions needed to set that Light, then each light would go though a Timer with your pulse rate, then out to the DO.
Max Resolution of the Pulsing Timer in a Brain is 0.1 seconds since Mach scans at that same rate.
scott