E Ink Paint

When I was a child, we used to have a wall (under the staircase) that was painted with blackboard paint, so I (and my brother) could draw in chalk on it.
These days we all have whiteboards with erasable colour markers (except mathematicians that don't mind the chalk dust apparently ;-) However, whiteboards (and walls covered with a similar material) are really hard to clean: a coloured stain always remains, and often a vague shadow of the original drawing/sentence/formula remains visible as well.

Perhaps we could make use of E Ink technology? In E Ink black and white coloured particles (with opposite charge) are captured in microscopic transparent capsules, such that applying a positive or negative charge moves the black or white particles to the surface. Allowing one to create any black and white image when such  E Ink capsules are aligned in a kind of grid.

Couldn't you turn that into a kind of paint? So you could draw on a wall covered with such paint with a marker that makes the black charged particles come to the surface, while the opposite charged eraser would make the white particles come to the surface? If the capsules where small enough, alignment in a grid wouldn't be necessary really, as long as the capsules are spread evenly and dense enough...