Here's an old thread about hooking up a bare 4-wire, 3-aspect LED signal head to the Lionel IR "ITAD". Lots of detail about the actual yellow-green delay circuit used in the MTH signal head(s) and how to modify it to apply to a 4-wire LED assembly.
https://ogrforum.ogaugerr.com/...al-with-lionel-153ir
The thread also shows the inexpensive "wehonest" 4-wire, 3-aspect LED signal head and controller board which has the yellow-green delay function. Their controller board even has what amounts to a built-in ITAD-like occupancy detector. If you already have an ITAD, you could use the ITAD instead to activate the LED sequence. Photo from thread copied below:
A separate OGR thread showing other bare wire signal heads from "wehonest":
