You have accomplished the difficult part: identifying the various leads (wires) and how the lamps are wired. Now you just need to take a look at a few websites. There is one by the man (Mr. Terry Christopher) who was the original designer of a line of signals and whose line of signals and control circuits are now sold by Atlas.
Depending upon how prototypical you want you operation to be, you can pretty much design your own system of signalling for your railroad. There are several companies that make signal control circuits or you can design you own. You can make the system as simple or as complicated as you want.
