[Quoth]

4000 colours is a misnomer. That's the total of all shades, hues and saturations. Also pastel to improve brightness.

Simulated cheap wood pulp comics. No use for decent illustrated books.

Colour eink is tiny niche.

Even basic LCD is 16 Million and HDR is more. The colour enk is so poor and needs so much LED light that decent LCD already out classes it. The amount of front light needed, especially for larger panels, dramatically reduces the advantage of mono eink over LCD.

The future for larger colour mass market devices to read on isn't eink, unless there is a dramatic new technology. It's better tablet LCD panels like NxtPaper, as already exists on 23″ to 32″ 4K HDR desktop screens.

Any approx 13″ Kaleido or Gallery based ereader will be lower resolution than a decent tablet and there will be LCD tablets with no eyestrain. My 23″ desktop 4K LG HDR LCD has no eyestrain, excessive blue, flicker or glare.

If a panel also uses quantum dots for red and green (so called QLED, which are really LCD) then it will also be be able to be bright enough for outdoor use.

I'll be amazed if there is ever a successful and usable Gallery 3 based ereader, though one company is trying. Gallery 3 is similar colour rendition and range to High Color 16 bit graphics 30 years ago. Certainly better colour than Triton or Kaleido, but still about x10 to slow for a page refresh.