Users with many forms of color-blindness can't distinguish between the different colors of the round, red yellow and green 'traffic' light icons. It would be preferable to use different graphic logos (such as the existing error/warning icons, or a circle with a cross/exclamation mark inside it) or have some text in addition to the icon indicating the severity of the audit result.
Closing as invalid, as this bug pertains to the old inspector UI and/or its tests. Please file a new bug (https://www.webkit.org/new-inspector-bug) if the bug/feature/issue is still relevant to WebKit trunk.