I checked a few other versions.
The SNES version does not have that "acid in tubes" look on that level, even though in general the levels look similar to the Amiga version (or more accurately, like the Lemmings Solution screenshots).
The Genesis/Megadriver version of Lemcon is redesigned to take less space, so the entire part left of entrance is effectively removed and replaced with something simpler with no acid.
The Windows version, in general, apparently looks exactly like DOS Lemmings.
The Mac version is hi-res only, but to my surprise, it
does have the same "acid in tubes" look:
(yes, they did botch it up a little, with the "wavy" parts in the stack still exposed)
So I'm not sure where exactly the screenshots for the Lemmings Solution came from.̆ I'd like to try out the Atari ST version but I'll have to download it from somewhere along with a suitable ST emulator. ̆It looks like the "acid in tubes" look is in a few selected versions but not many.