Stan,
I found my MTH traffic signals, a two signal set that I was thinking was a four signal set? Also, it was in a type of blister pack and I was thinking it was in a box. I also ordered some of the We_Honest traffic signals. It appears all I have ever ordered were the dwarf signals for switch positions? Both of these items are a bargain! Quality is good too, at least on the dwarf signals I have.
Also the MOSFETs seem to be MIA, still have not arrived so we still have only the transistors to fiddle with. 
It appears that the MTH signals are common cathode so modifications would need to be made on the common anode PCBs we have from the current project. I would be willing to make another PCB for these, if the current ones can not be made to work with both types of signals.
The wire colors on the MTH traffic signals are as follows:
Green - Common Cathode
Blue - Green LED
White - Yellow LED
Yellow - Red LED
One thing MTH thought of that I did not is an 'On-Off' switch on the signal controller PCB/Controller. Might be a good idea for an addition to the PCB.
Something interesting turned up while fiddling with the MTH signals, I lowered my DC power supply to 3 volts and tested the MTH signal LEDs directly without their controller. The current 4 wire circuit using transistors (per Stan's earlier recommended revisions) was still on the bread board and also being powered. It was working on 3 VDC! The lights were not quite as bright, but it was still working! 3 VDC might be a bit low, but I am now wondering if instead of the 9-12 VDC I was previously using, 5 or 6 VDC would be sufficient and I should switch to that permanently?
Here are some pictures of the MTH traffic signals for you, for reference, if you don't have them already. Also, not sure what type of connectors these are? Maybe someone will be able to ID them and post the info?
Added later after more fiddling: I don't know what those large resistors shown in this picture are doing, but they get pretty HOT!
