First off, the auto paint store could not match the green paint based off a small chip sample so I printed a large example for them to use. That was a real challenge in itself because just altering the print quality from normal to best would make it an entirely different green. Trial and error got me this which ended up being RGB 55-70-50. I'll try to get the paint made again tomorrow.
Secondly, I sorted out how to utilize the light panels to best advantage. What works is making a sandwich of the smoked acrylic, the graphics, a diffuser, and another 1/8" sheet of clear acrylic. In the example here, I used a sheet of paper as a diffuser, but will use a very thin sheet of Styrene later unless the graphic prints are made with a diffuser included. The light panel is then set behind that at the maximum distance to fit in.
Ignoring the tape shadows and paper grain, you can see it lights evenly now.
The light panel will rest on bits of Styrene that hold it in place but also don't prevent getting the acrylic pieces and graphic in.
Lastly, I ordered a sample of Duratrans backlit graphic material from Blue River Digital. I'm expecting this will work given their description.