(semi-offtopic) Isn't there some kind of glass slab that turns any light emitting display into a color e-ink like display? Isn't there a theoretical model at least?
There isn't. You can try sensing the incoming light with some kind of transparent light sensor matrix, like MIT's BiDi screen [1], which enables mimicking a diffuse reflector (i.e. paper) under ambient lightning, but there's no linear material that will do that.
