The version of Tank you've described dates to Laserium I. The blue and green scan glasses were common diffused Plexiglas of the time. The yellow looked like it was made/molded from some sort of embossed decorative glass. Basically the yellow looked like a coarse fresnel lens.
Laserium used a single sided pebbled Plexiglas for a lot of effects over the years. I think it might have been P5, but I've never been able to source it in the last decade. Everything is a finer pebble and isn't actually flat on the "flat" surface.
Whittemore-Durgin Glass Company has a "granite" art glass that's better than the Plexiglas I've found to date. I've toyed with using my little CNC mill to machine Lumia, but that's way back burner...
"There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso