I suppose I don't understand how colors work on e-paper at all. Can these 7 colors not be dithered? Or even mixed more properly, for something like true color functionality?
I use Floyd-Steinberg dithering, and if you look at the "More images" section you can see it does a reasonable job at representing colors. Also worth nothing that 2 of those 7 colors are black & white, so questionable naming perhaps.
I'm pretty sure real production use cases of these screens don't tend to use dithering though, focusing on contrast and readability.
The naming is a hard problem - black/white/orange and black/white/red screens are commonly called 3-color screens, to distinguish them from normal black/white screens. Calling them 1-color screens would be an awful choice of name, but "7-color screens" is a name consistent with the "3-color screens" name and calling them 5-color would be horribly confusing (especially since current 5-color would become 3-color).
Also, black and white are their own specific primary colors, they're not made out of a combination of other colors, so it's rather appropriate to call them colors in that context.
