There’s a lot more to “accessible design” than audio access and alt text. How about color accessibility? If it’s not something that you immediately consider you’re not alone, but for those affected it’s a really big deal. As counter-intuitive as it sounds, It is not inclusive to use color as a way to communicate information. Let me explain.
There are basically two accessibility issues related to the choice of color for digital design:
The first is that many people are unable to perceive color differences, or they may perceive color differently than the general population. Red/blue color-blindness immediately comes to mind. It is very important to avoid using color alone to communicate information. This holds true for digital and print media.
For example, on a website or digital document if link text is blue it is oftentimes underlined so users who are unable to perceive color differences can distinguish the links from surrounding text. This is an accessibility feature that has been around for a long time because it was originally used to aid non-disabled readers in using and understanding links when they were a new thing. As an unexpected bonus it serves as an aid to those with color vision deficiency as well.
The second way that color accessibility can be a problem is for people who have difficulty perceiving text if there is too little contrast between the foreground and background of the image. The W3C Web Content Accessibility Guidelines require that color combinations meet clearly defined contrast ratios. In order to meet the guidelines at Level AA, text or images of text must have a contrast ratio of at least 4.5:1 (or 3:1 for large text). In order to meet the guidelines at the stricter Level AAA, the contrast ratio must be at least 7:1 (or 4.5:1 for large text). This Wikipedia Manual of Style does a good job of explaining the differences.
The World Health Organization estimates that about 217 million people live with some form of moderate to severe vision impairment. That statistic alone is reason enough to design for accessibility. Those numbers represent a huge audience no matter what the industry. Color accessibility enables people with visual impairments or color vision deficiencies to interact with digital experiences in the same way as their non-visually-impaired counterparts, and that can only be good for business.
Let’s not forget either that in addition to accessibility being an ethical best practice, it is the law. There are definite legal implications for not complying with regulatory requirements around accessibility and the rise in inaccessibility lawsuits continues unabated.
There are many online tools and reference materials available to assist in the creation-of or upgrade-to a website, app or other digital presence. The University of Washington has a lot of good information about accessible technology here, and about the effective use of color here.