The Dogma W4 - details and explanation

Ad 11. The colors

The use of colors in a web document must be specified with adequate attention to contrast between foreground and background hue and brightness.

Applicable guideline for choosing contrasting colors is converting them into the greyscale (0 % means black, 100 % is white). Sufficient contrast between foreground and background is then accomplished by choosing colors, the values of whose, in the greyscale, differ in more that 50 per cent. In addition no color combinations, which handicap users with color blindness (see ColorBlind ColorLab, ColorBlind Webpage Filter), may be used.

Furthermore, no background pattern should be used which decreases the legibility of the document's content.

When the background is made of pattern or picture, the rule of sufficient contrast applies to all single points of background.

Rules for the text and its background applies to the text with any informational value contained in pictures and other objects. Such text must be in one solid color; it is forbidden to use pattern, gradient or image.