It's not. They have 4k colors available. Good enough for an eink reader, not good enough for art display.

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.

You could commission works that exploit the medium.

This sounds like the answer. Retro-looking CGI will be right at home on a canvas like that.