This is a commonly used foam for working with light (more generally referred to as "LED foam"). It diffuses light, is lightweight compared to translucent plastics, and can be heat treated like other EVA foams. The greater its thickness, the more the light is diffused and the lower brightness you achieve.
We recommend painting with an airbrush and transparent paints that allow light to pass through, or applying a very thin layer when using regular paints. Shape at low temperatures (melts easily) and glue with clear glue for best results.
The edges of the foam may have manufacturing defects. You will get a slightly larger foam than advertised.