Try searching for "Daltonize." These tools let you see what your image would look like to someone with red-green or other color blindness. It is not just about color choices or ramps, it is about contrast and what colors abut each other. The tools might be able to directly fix a JPEG, but they don't work with ArcMAP.
508c compliance is way more subtle and complex than an app. (You could say that about so many things.) I took a very time consuming 1-unit class in Web compliance several years ago. There are lots of things to look at, but a compliant site is better in many ways, such as being easier to find and to search and to maintain.
