LED Light to Toggle Switch

Not to duck your question, but have you considered just using a green led lighted toggle switch which will light up green when each track is powered on ?

They are available on the big A and rated at 12 volt. If you are running command at 18v and using track power, a diode can be installed to reduce the voltage so the led doesn't burn out. 

Ritchie I never new they made such as a lighted toggle switch.  I bought the toggles at local hardware stores.  If I was ever going to make another control board, that is the way to go, plus saves time and money.

Where is a Big A store?

Amazon - search 12v green led toggle switches - usually sold in batches of 3-5 toggles. At less than $3/per switch and depending on how many you need, it might be worth the time and effort needed to wire in separate led's to just get these and save the others for another project. 

Here is another alternative.  These track power indicator lights can be integrated into the track bumper.  These light poles can be purchased from a number of suppliers- these are from ebay and a seller named wehonest, yes, that is the name you can search.   If you do something like this you will need to include a resistor to make sure the LED receives the correct voltage and current.  Here is one of many possible links to a calculator for that.  All the wiring and resistor are located under the layout.

Here are the markers with the whisker track numbered.  I should have turned them on.

Here is mission control to turn on the desired whisker track.  "table" powers the track on the table and "turn" controls the rotation

A better shot of one of the led light poles.