Avoid referring to a button, menu, or other item in the page only by its position on the page; instead, use additional information that describes the content.
Referring to a specific item in the page content by only its visual position prevents people who use screen readers from being able to make sense of this visual description. Another downside to referring to items by their position is that their position might change when the page is viewed at different screen sizes, such as on a smartphone....
Some people with color deficit have trouble differentiating between specific colors, such as between red and green or red and black. Screen reader users do not access content visually, so they do not have access to color information.
Color is a powerful visual means of presenting or distinguishing information, but when you use color to identify or distinguish information, make sure that this information is still available to people who can't perceive color.