If you look at an e-ink display under a microscope you'll see that the "pixels" are more like "shards" of variously-shaped cells.
https://twitter.com/sqfmi/status/1178018736684580865
The "pixels" are made of the actual addressing grid that creates the currents that attract the pigment in the capsules.
This is part of what ends up giving the appearance of a higher-resolution display when rendering text, as you get some softer edges "for free." (And it's what makes the display look 'blurry' for some viewers.)
So, to your question, there's currently no attempt with the technology to precisely place the colors on the display. The capsules are just spread all over, and the grid does the work.
Rods in eyes aren't on a regular grid anyway, why should it matter how the pixels are distributed as long as they cover the plane and are mostly uniform?
So instead, each cell is capable of displaying any color, and they've got a more complicated refresh mechanism that they use to "write" to them.
And the upshot of that is listed in the specifications from the linked page: The refresh time on this display is 15 seconds. Which is far, far away from where it would need to be in order to be a practical option for color e-readers.
- https://www.eink.com/assets/img/technology/GIF_Cup_E.gif
- https://www.eink.com/assets/img/technology/GIF_ACeP_E.gif
Refresh rate was always an issue, but it is gradually improving. For static reading it's not a problem.
If there was a way to mix the inks and have them 100% separate by the grid on demand, it could be possible.
It’s fun to imagine Jesus returning in 30xx AD but this time instead of absolving the world of its accumulated sin he wipes away the accumulated technical debt of 1.5 millennia worth of corporate IT
Hell, since the writer was omnipotent and omniscient, the code was even built with the ability to perfectly modify itself when the company changed the DB on September 12, 2011 at 3:24 in the morning.
So any projects started since 2008 that were written without Py3 compatibility had known tech debt they were choosing to take on.
My point is this is a very different situation from the Python 2->3 transition.
If you have 12 years' notice to make some changes, I don't consider that technical debt: that's the normal price of maintaining software in a changing world. It's not "debt" that costs "extra interest" to pay back for questionable choices made previously.
I’m not sure that current “transparent” oled technology is transparent and thin enough though.
https://www.pcworld.com/article/165724/bye_bye_kindle_netboo...
https://arstechnica.com/gadgets/2011/04/apple-exploring-hybr...
These are unique advantages to e-ink as far as I’m aware.
Also where did this stationary context come from?
You can easily have a non backlit black and white display, like the one on an f91w or LCD clock.
Of course, you could simply make a matrix of tri-tone capsules, with white, black and colour. Then you have the contrast ratio and the colour space advantages. I don't know why this hasn't been done, I'm not an expert on e-Ink!
The microcapsules are not individually wired up to anything, so I don't think it's feasible to make each color channel independently addressable. Instead, a grid of wires behind the capsules are either positively or negatively charged, in order to attract or repel the charged colored particles in each capsule. There are only 2 charges, but by using different sizes of particles for different colors, you can finagle it so that the color you want ends up on top.
If they could address capsules individually, that would also increase the possible resolution of a black-and-white display; they'd do it if they could. But since the mechanism is about attracting and repelling charged particles, there's probably a pretty hard limit on how much you can increase the resolution before there is interference between neighboring pixels.
Would that still look like paper, though?
Sure, it'd look like badly-registered offset printing, but that only matters for small up-close displays, not large far-away displays. (And you could fix the registration with a precisely-cast diffuser layer, convolving each subpixel-cluster.)
If this was for reading rather than imagery, and you wanted to have true blacks, you could also just step one level forward in e-ink technology, and have the colored micro-capsule groups be just dual-tone (the capsule's color plus black), giving you {C+K, Y+K, M+K, K} bitplanes.
Are e-ink display manufacturers just imprecise in the way they deposit the capsules into the panel, making it impossible to address individual capsules? (If so, that seems like something that could be solved pretty easily with modern photolithography processes, e.g. etching onto the backing electrode a grid of "buckets" for individual micro-capsules to fall into.)