When designing a website or web application there are over 16.5 million options for possible color combinations. Insufficient color contrast prevents users with color deficiencies or low vision from reading and distinguishing content. WCAG 2.0 level AA and the proposed Section 508 Refresh require a contrast ratio of 4.5:1 or greater for text of less than 18 point, and 3:1 for text of 18 point (or 14 point bolded) or greater.
There are several free tools available for analyzing color contrast including WebAIM Color Contrast Checker. Also preview SSB BART Group’s Web Accessibility 101 Series video on YouTube.