It is coming: a waveshare 7 color eink screen is $600 on aliexpress, 16 second refresh
If partial refresh comes more supported in open source, pictures could be drawn immediately with the b&w text, then refresh little by little to add color.
There are a few "color eink" displays floating around in demos which are actually just an lcd with a matte layer over the top.
Just look at the announced resolution in dpi in b&w vs color, and you'll see they use a LCD mask in front.
If you want both color and eink, it's better to get a dual screen, like a Lenovo C930 book: use the screen clone mode and just turn off the color screen when you don't need it.
This can also gives you a eink laptop if you use a USB keyboard.
I've also toyed with the idea of purchasing an old Surface Pro 3 because of the price and the ability to run a full Linux distro—though obviously, I lose all the benefits of e-ink with this option.
For the keyboard, consider getting a USB or bluetooth keyboard, like Lenovo ThinkPad TrackPoint Keyboard II, or ThinkPad Compact USB Keyboard with TrackPoint (0B47190) - they are very comfortable.
As for linux support, check out https://github.com/aleksb/yogabook-c930-linux-eink-driver
They're a lousy company that does not respect the GPL and ships intentionally insecure software (ancient linux kernel with SELinux disabled for starters) that phones home to Chinese servers. The bootloader is locked, so putting pmOS is out of the question and their update files are intentionally obfuscated.
I explain it all in this comment: https://news.ycombinator.com/item?id=21041543
This received some attention in the re--it community last month--the company still does not care [1]. It's a tragedy because their hardware is good, otherwise and they can compete on that.
In other news, I am now a happy owner of a ReMarkable 2 and the first day I was able to SSH in, set up rsync on my local network and customize the hosts file to disable their cloud services. We should not tolerate the inability to run software on computers that we own, especially for devices that are as trusted as notebooks and personal computers, which this tablet is.
I'm not sure if I should sell my Boox Note or relegate it to use as signage. The only problem is that if the battery dies, it refreshes the display to a "battery depleted" screen, instead of leaving up the last image. But you can't customize that because the bootloader is locked.
Edit: Another note about Onyx. At least my Note does not support proper C2C charging. In other words, you can't charge from a Type-C charger, you have to use a type-A charger. My rM2 works just fine with all of my C2C chargers.
[0]: https://news.ycombinator.com/item?id=24237328
[1]: https://old.reddit.com/r/linux/comments/hl09g7/onyx_boox_chi...