Wednesday, April 14, 2010

Testing Colours to Enhance Web Readability

According to the University of Washington’s Department of Ophthalmology, 2.8 million Americans are colour blind, which can express itself in many variations and degrees of severity. Colour perception problems are important considerations when developing web sites to ensure that all users have access to the content and the functionality of site.

Based on the contrast ratio algorithm, Level AA conformance requires text to have a contrast ratio of at least 4.5:1; larger text (18 point font or larger, or 14 point or larger if bold) a contrast ratio of at least 3:1. For Level AAA conformance, text requires a contrast ratio of at least 7:1; larger text a contrast ratio of at least 4.5:1. Incidental text or images of text that are not part of the user interface or are purely decorative and text that is part of a logo or brand are excluded from the colour contrast requirement

DIY conformance testing tools are available for Windoze and Mac OS X.