Keep in mind that 1 in 200 women and 1 in 12 men are color blind. The persona here will be a male and we'll call him Sam. He has a Red-green deficiency in his eye sight. (Meaning reds, yellows, oranges, and greens end up appearing as various shades of yellow. Reds may appear as black.)
Your site is designed using a lot of warm colors. Sam can't distinguish the colors because they are in a color range he can't see, everything is muddy and can't tell where to look. He gets frustrated and leaves the site.
One would think it would be impossible to use the Internet if one was blind. It's not and with the help of you, the experience can be pleasurable. Sally has been blind since birth and never really had access to a computer. Her school requires some assignments to be completed on the Internet. She sits down at a computer with a keyboard and mouse. The computer has been configured to use text-to-speech and a screen reader. As she navigates with the tab key, listening to the computer's feedback, she's able to get to her course website. She can't figure out how to navigate because the semantic structure of the site isn't built with best practices and doesn't utilize aria attributes to aid the browser screen reader software. The tab order of the site is also unuseable. She's lost, upset, frustrated, helpless, and anxious. She keeps trying to find where she needs to go and eventually gives up and asks someone in the room for help.
The web is definitely more friendly to those who can't hear, since one can see where they need to click and navigate to, but another set of challenges surface. The consumption of audio and visual content becomes impossible and quite frankly, useless to the viewer. Beet watches YouTube videos all the time and is able to follow along with the visuals because someone has written out subtitles to go along with the video. There's a few Facebook videos that also provide transcripts which also allows him to follow along. Without video transcripts, the user doesn't have context to the visuals in front of him.
The elderly and those who are new to computers have similar challenges so we'll be talking about them together. Phyllis has a hard time seeing and her confidence level with computers and the web is next to none. She's afraid of every pop up and unexpected action. It causes anxiety for her. Those dang kids and their good eyes cause text to be smaller than what she can read screen. She has trouble with low contrast text, small type, and not knowing what button to click to do what she wants. (Same goes for the new to computers audience.) She either calls her nephew to help her or throws the computer out the window out of fear and frustration.