This uses E Ink's Kaleido display, which uses colored pixels (subpixels) to create color. Subpixels are standard for emissive color screens, but for reflective screens they result in very dark images (and consequently very low contrast) compared to paper.

For example, to display a red image, the screen simply turns the green and blue subpixels black. So two thirds of the screen area is black and only one third is red. For printed paper the whole sheet would be red. And to display white, the subpixels can't turn white (they can only turn black), so they have to mix white from red, green and blue. So each subpixel only reflects around a third of the visible spectrum, while for white paper the whole area reflects all visible wavelengths. Making the colored Kaleido screen very dark in comparison.

The problem is well known. If you want acceptable contrast in a color e paper screen, you need a display technology which can change colors inside the pixels, not just the brightness. E Ink does have such technology, but it is very slow and offers only very few colors.