How color e-ink works
Nothing on a color e-ink screen glows. Each pixel is a tiny cup of colored pigment in clear fluid, and every picture is built from dots of six colors.
Electronic ink
Classic E Ink is made of millions of capsules, each about the width of a human hair, holding charged black and white particles in clear fluid. An electric field pulls one color or the other to the surface, and once there they stay without power. The display is bistable: only pixels that change need energy. It reflects light like paper, so it needs no backlight (E Ink).
Inside a Spectra 6 pixel
Every color frame in our comparison uses E Ink Spectra 6. Display distributors describe it as microcups, each holding four pigments (white, red, yellow and blue) that together show six colors: black, white, red, yellow, blue and green (LCD-Mikroelektronik, August 22, 2025). The voltage under each cup decides which pigment comes to the top.
E Ink quotes up to 200 pixels per inch, a typical contrast ratio of 30:1 and an operating range of 0-50 °C (E Ink Spectra 6). The technology was designed first for shop signs and posters, which is why its colors are bold rather than subtle.
Six inks, dithered
A pixel can only be one of the six colors, so every other shade is faked by mixing dots, the trick newspapers use. The usual method is Floyd-Steinberg error diffusion. Take each pixel in turn, pick the nearest of the six colors, work out how far off it was, and push that error onto the pixels to the right and below: 7/16 to the right, 3/16 below-left, 5/16 below and 1/16 below-right. Across an area, the dots average out to the right color. Waveshare recommends this method for its Spectra 6 panels (Waveshare manual), and frame makers use tuned versions of their own; Aura says its algorithm gives the look of millions of tones (MacRumors).
The same happens to a real picture. Below is a patch of Van Gogh’s Wheat Field with Cypresses (The Met, public domain), before and after our photo converter, which runs Floyd-Steinberg in your browser.
That is why e-ink photos look grainy up close, like film, and smooth from across the room.
The inks are duller than a screen
- Black
- White
- Yellow
- Red
- Blue
- Green
Real inks are duller than pure screen colors. Pimoroni’s open-source driver for its Spectra 6 displays lists measured colors beside the pure ones: its white is a light gray (RGB 161, 164, 165) and its blue a dark navy (61, 59, 94) (Pimoroni inky library). The chips above show both, pure on top and measured below, and our converter’s “muted” preview uses the measured set.
Why a refresh takes so long
Changing the picture means physically moving pigment through fluid, several times over, to get each color right. That’s why frames flash and shimmer for a while: about 20 seconds on Bloomin8, about 30 on the Aura Ink, 15-30 on SwitchBot, and up to a minute for InkPoster’s first image. Waveshare quotes 19 seconds for a full refresh of its 13.3-inch Spectra 6 panel. It’s also why frames change picture once a day or less: every refresh uses battery.
Other kinds of color e-paper
| Technology | How it makes color | Where you’ll see it |
|---|---|---|
| Kaleido 3 | A color filter over a black-and-white panel: 4,096 colors at 150 ppi | Color e-readers and notebooks |
| Gallery 3 | Four particles (cyan, magenta, yellow, white) in each pixel, 300 ppi | E-readers and notebooks |
| Spectra 6 | Colored pigments showing six colors, up to 200 ppi | Signs, shelf labels and art frames |
Source: Good e-Reader (August 25, 2026). Kaleido colors are more muted because the filter sits over a grayscale panel; photo frames use Spectra 6 instead.