Measurements & formulas

Color confusion lines

Lines in a CIE chromaticity diagram that intersect colors that are difficult to distinguish for people with color vision deficiencies.

The point where confusion lines converge is the copunctal point.

Protan
Choose an image
 Select a deficiency type to preview confusion lines. Sample colors shown along confusion lines with simulation to demonstrate color appearance for the selected deficiency type.

How it affects UI design

Some color tools provide visualization of color confusion lines to assist in color picking.

Confusion lines alone are insufficient for determining "safe" colors. Additional analysis of simulated colors should be done using the color difference formula (Delta E).

Sources:

  1. Individual Differences in Color Vision. Color Usage Lab, Nasa Ames Research Center. https://colorusage.arc.nasa.gov/indiv_diffs.php
  2. Color perception. Webvision.med.utah.edu. https://webvision.med.utah.edu/book/part-viii-psychophysics-of-vision/color-perception/
  3. Daniel Flück. Colblindor. https://www.color-blindness.com/2009/01/19/colorblind-colors-of-confusion/