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.