Many thanks to all of you for digging into this!! After seeing the photos posted by @dutchzcarguy I can confirm these individual "icons" used to work perfectly. I was always able to see the individual "STOP", "HEAD", "TAIL", "WASH", "BATT" and finally "OK" at the end - all in different colors.
I don't think they are LED's since this is early 1980's technology. In the photo posted by @dutchzcarguy the only "icon" that I never see is the solid color "DEFECT" signal. I think that's good news. The layered glass is an interesting technology that's likely very unique to the Japanese engineers. And like Captain Obvious said, "It's a light pipe." Something like some early fiber optic technology.
This has been a very "enlightening" (HA HA) discussion. Now that I see photos of the WARNING MODULE (thank you very much!!) I know what I'm looking for when I get under the passenger side of the dash. There are tons of wires over on that side of the dash . . . very close to the fuse box. Now that the weather is getting nicer, I can pull my Z out of the garage on a dry day and start looking. I also have tons of photos which I will go through.
Another thing BTW! I have ordered an enclosed trailer, currently being assembled by ALUMA in Iowa. 8.5 feet wide, 18 feet long with a dovetail at the back door ramp. I put a healthy down payment on it, but that was before the stock market took a sharp nosedive. Now I'm concerned that many spring and early summer car shows are going to be cancelled because of the pandemic. I'm hoping to take delivery on this trailer in early May. I checked yesterday and their company is considered "essential" because of all the agricultural trailers they make, so I hope there won't be delays and I hope the car shows will go on as planned. HOPE.
Thanks for all the great and helpful discussion! Keep it going! I'm determined to get that warning module working. Rich K = Car54280ZX. I will keep everyone posted!