One-Bit video playing on the memory-display:
https://youtu.be/zzJjE1VPKjI?t=73
Black and White-ish grey only, but very crisp and readable. They're used in a lot of smart-watches, low-power instrumentation, etc. And it's sooooooo tiny. For a second screen on an e-ink tablet, I like the fact that it's a perfectly usable UI area but won't compete with the main screen or be that noticeable when it's blank - it's just a bit of rectangular space appropriately sized for a small information tag below the "printed image" above on the canvas -- something like a museum tag set between two small knobs, a blank space where information appears when needed and only when needed.
A nice video demonstrating and explaining the little displays:
https://www.youtube.com/watch?v=eAoC818Mxy4