The Kaleido panels features in this article indeed do 4096 colors, but the Spectra 6 panels also from E-ink can be a bit more - they mix particles of 6 different primary colors, and with some advanced dithering in place you can get pretty impressive results that really look quite pleasing.

Still, there's a lot of details to consider and trade-ofs to make wrt/ content, and Spectra refresh is also dead-slow.

Perhaps to their credit, E-Ink isn't even trying to hide the refresh in their marketing material: https://www.youtube.com/watch?v=Hr_EQaqTK0M (second half has a lot of examples of poster-sized Spectra 6 and Spectra 3100 panels).

Not all art would work but you could definitely find works that could work within the constraints.