  Over 300 million people who live with color vision deficiency (CVD) have a
decreased ability to distinguish between colors, limiting their ability to
interact with websites and software packages. User interface designers have
taken various approaches to tackle the issue with most offering a high contrast
mode. 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 the absence of subjective data, we aim to investigate how a CVD
observer might rate the functionality and aesthetics of existing UIs. However,
the design of a comparative study of CVD vs. non-CVD populations is inherently
hard, therefore we build on the successful field of physiologically-based CVD
models, and propose a novel simulation-based experimental protocol, where
non-CVD observers rate the relative aesthetics and functionality of screenshots
of 20 popular websites as seen in full color vs. with simulated CVD. 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. While our results are only valid in the context of simulated
CVD screenshots, the approach has the benefit of being easily deployable, and
can help to spot a number of common pitfalls in production. Finally, we propose
a AAA-A classification of the interfaces we analyzed.
