Measuring User Interface Accessibility for Color Blind Users

Color vision deficiency (CVD, color blindness) is the failure or decreased ability to distinguish between colors under normal lighting conditions. There are over 300 million people worldwide with CVD, including approx. 1 in 12 men (8%) and 1 in 250 women (0.5%). CVD can limit a user's ability to interact with websites and software packages that are otherwise basic commodities. User interface designers have taken various approaches to tackle the issue with some interfaces offering a high contrast mode, and others integrating color-blind awareness into their website design process. The Web Content Accessibility Guidelines (WCAG) outline some best practices for maintaining accessibility that have been adopted and recommended by several governments; however, it is currently uncertain how this impacts perceived user functionality and if this could result in a reduced aesthetic look. In our work, we present a subjective user study to measure the loss of functionality and aesthetics as potentially seen by CVD observers for 20 popular websites and software packages. As recruiting participants with CVD is non-trivial, we developed a simulation-based pipeline instead for our full-reference mean opinion score experiment, which as far as we know is a novelty in the field. Our results show that relative aesthetics and functionality correlate positively and that an operating-system-wide high contrast mode can reduce both aesthetics and functionality for CVD users. Finally, we propose a AAA--A classification of the interfaces we analyzed.