I wonder why they did not add color e-ink to the Kindle Scribe. Maybe they thought the price would be prohibitively expensive?
But a bigger difference is that Gallery 3 uses CMYW pigments; there's no black pigment, rather the microcapsules themselves are tinted black on one end, so the black ultimately ends up a little impure. Also there are only 4 shades of grey for antialiasing rather than 16.