Have you checked this one out? Not associated with them but I do own a Boox Max Lumi (not color) and just saw the announcement about this.
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