Chromaticity: guidance for accessible visualization color design
Chromaticity: guidance for accessible visualization color design
Chromaticity is a color design assistance tool that makes it easier to manually create color palettes for visualization while minding discriminability and accessibility.
In Chromaticity, you can pick your own colors from four color spaces (Lab, LCh, Jab, and RGB) or pick them from an image of your choice. Then, Chromaticity automatically provides information about your palette’s discriminability, color vision deficiency accessibility, and also provides reconfigurable visualization previews. Chromaticity supports both categorical and sequential palette design.
Chromaticity supports color picking in three perceptual color spaces as well as in RGB.
Two of the perceptual color spaces are CIELAB color spaces (Lab and LCh), which position colors based on how the human brain processes color. Lab colors are defined by their lightness (L), redness-to-greenness (a), and blueness-to-yellowness (b). LCh colors are also defined by lightness, but then are defined by chroma (colorfulness, radius) and hue (angle). In both CIELAB color spaces the farther apart any two colors are the more discriminable the two colors are.
The third perceptual color space is Jab, which is similar to Lab; however, Jab uses an updated color appearance model that in theory provides greater precision for discriminability measurements. This space still hasn’t yet been tested within the context of visualization design and is mostly for providing designers another representation of color that may improve color selection.
If you’d like to know more about CIELAB and Jab, there is a high level overview of each here.
Chromaticity provides discriminability estimates in several ways: a customizable visualization preview, a discriminability table that shows warning signs for poorly discriminable colors, and by eyeballing the palette preview immediately below the color selection area.
The color discriminability table also shows discriminability warning signs for a variety of color vision deficiencies. Note that, like the Jab color space, these estimates have not been empirically tested and should be viewed as guidelines opposed to being fully accurate warnings.
Chromaticity was born as an idea from two sources. The first source of inspiration came from developing Colorgorical, where I noticed how difficult it is to create perceptually-grounded color palettes by hand. The second source of inspiration came from an IEEE VIS panel a few years ago with Georges Grinstein and a few others, where they discussed the lack of accessibility research in the information visualization community. More recently, I think that Chromaticity also riffs on similar discussions in the OpenVisConf community.
While Chromaticity is not empirically-tested, I hope it still helps designers become more mindful of how their color selections will appear to their entire audience.