Hm, why do you have 3 groups and not only 3 lights? And what are groups for you? Do you have multiple lights for red?
If all lights of one color do the same at the exact same time, then you can just plug them into the Set Visibilty nodes of the other red/green and yellow
lights that are already there (or create a new node for every light :X). You could also pack them into an array and go through the array, but that is just
a things of structure and organization.
If all lights of one color work seperatly from each other, then you need to wrike a function for each with the time you want.