In order for your site to be 508 compliant, it must pass a set of rigorous and, to be honest, subjective set of guidelines. One of the more interesting ones is it cannot convey color as meaning.
The actual guidline in lawyer-speak: Color coding shall not be used as the only means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.
What does that mean? Basically it boils down to this: each page must be understood even if it was black and white. Persons with visual impairments must be able to understand the content. ‘Follow the red text to find the answer’ with instructions in red is forbidden. The easiest way to know if you pass is to print each pages (yes, each page) and test if it is understood void of any color.
A pain? Yes. Tedious? Yes. But if you want to pass, you have to manually check.