Shroomite Plating Wall

The glow is the point. Placed behind a room it lights the space by itself, which makes it a good pick for builds where torches and lamps would break up a clean surface. A later patch tied the light color to whatever paint you apply, so you can pull a whole room toward blue or green without adding a single fixture.

Visually it lands close to the plain Mushroom Wall. If you only want the look and not the lighting, the cheap option gets you most of the way there and does not cost you Chlorophyte.

It also carries one of the deepest Shimmer decrafting chains in the game, roughly on par with the Zenith. That is a curiosity more than a use, unless you are deliberately unwinding materials back down the tree.