Museo&WebPlanning Kit for a Quality Site for Small and Medium Sized Museums |
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Use of ColourAppropriate use of colour is fundamental for accessibility. WCAG 1.0 in guide number 2, states “Do not base choices exclusively on colour” “Make sure graphics tests are visible when seen without colour”. Note two following points: 2.1 Ensure that all information conveyed with color is also available
without color, for example from context or markup. 2.2 Ensure that foreground and background color combinations provide
sufficient contrast when viewed by someone having color deficits
or when viewed on a black and white screen. The Italian Guidelines containing the technical requirements, the definitions of the different accessibility levels and the technical methodologies for the testing of Web site accessibility contains various criteria for the use of colour. The following algorithm- suggested by the W3C - can be used to calculate differences in brightness and colour between text and background:
Note that the algorithm is merely a guideline as it takes into account only the RGB (Red, Green, Blue) characteristics, whereas each monitor has its own brightness settings. You can easily test your pages using the following online tools
The most common type of colour blindness is difficulty in distinguishing reds, and the second most common is in distinguishing greens. There are various types of colour blindness:
The Colorblind
Web Page Filter <http://colorfilter.wickline.org/> is
an online programme for testing pages for accessibility in various
types of colour blindness. Useful tools Sample table of HTML colours with esadecimal values (italian version) |
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© Minerva
Project 2005-02, last revision 2005-04-21, edited by WP5, Committee for
the development of a prototype of public cultural websites. |