Few pieces of software recognize the needs of people with visual problems. From what I understand, Sonar was (is?) often used by the blind because of compatibility with a text-to-speech program, but that's different.
I consulted on a project once where the user interface was impossible to use if the user was color-blind. It had never even occurred to the company. Those of us who are fortunate enough to have our vision and hearing intact often don't consider what it's like not to have those faculties in full.
There are aspects of Sonar that could definitely be improved in terms of legibility with the tradeoff being more apparent visual clutter on the screen because more elements would be easily visible, and thus compete for your attention.