The results are in. I suspect almost any of those modules will work. I tried one of the opto coupled ones and one of the non-isolated ones, both worked fine. I'd be pretty sure that almost any of the similar relays would work as well.
Here's the two channel one, it has opto-isolation: C:US:3160" target="_blank">2-chan opto-isolated Relay Module
Here's the four channel one, it is not isolated, just uses transistors to drive the relays: C:US:3160" target="_blank">4-chan Relay Module
You need to supply the relay module with regulated 5V, a cell phone wall-wart is perfect for this. Other than that, you just need a series diode with the cathode toward the Fastrack switch indicator lamp lead to block the negative voltage. The relay is closed for positive voltages and open for negative voltages. Since it's a single form-C contact (SPDT), you can drive a signal when it's open and when it's closed for the two states (colors).
Note: the 4-chan relay says Optocoupler, but they lie, there is no opto's on the board. 
