Simpletest really needs to add an icon of some sort to the list of tests so that it is easier to find broken tests. We've addressed this in other parts of the UI & just need to apply it to the Testing infrastructure - admin/config/development/testing/results/3
As a practical example for how a user with over 20/20 vision can benefit from this, I reverse my screen colors so that I can work late at night and not disturb my partner when I'm working on bugs with Drupal. With the colors reversed I have no idea when there is a failed test or not as I can't distinguish easily by color.
WCAG reference is:
http://www.w3.org/TR/2008/REC-WCAG20-20081211/#visual-audio-contrast-wit...