Even though I read novels exclusively on my kindle, I would buy a color eink kindle if it were around the same price point as the current PW, for the following reason: some books, even novels, could be enhanced by color.
I read a trilogy and was a bit amazed to discover that the paper versions were using dark green, dark blue and dark maroon font, to match the three covers. This is kind of cool and different, but the cost of color print prevents this from being viable for most print novels.
Novels could be enhanced by colorful chapter numbers, colorful maps, etc., plus non fiction books would become interesting on eink devices.
They must have used multicolor LED's and finally realized it. ~ S. attempting to explain the colorful blobs on Kindle Paperwhite screens.