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.
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.