Understanding Accessibility
by Vivienne Trulock
Users of this site also found these sites useful
Guideline 2. Don't rely on colour alone.
Checkpoint 2.2 - Ensure that foreground and background colour combinations provide sufficient contrast when viewed by someone having colour deficits or when viewed on a black and white screen.
How do I do it?
If the foreground and background colours are too similar, they may not provide a good enough contrast for people with poor vision. Older people tend to have a more yellow vision so they may not always see what you do.
How do I check that it meets the WCAG criteria?
The purpose of this check is that partially sighted or colour blind individuals will be able to read the text on the background colour of the page.
An accessibility tool called aDesigner can be used to check this. aDesigner has 4 settings for low vision for which it can make a comparison regarding foreground and background colour combinations, including the three types of colour blindness, and crystalline lens transparency, or yellowing of the eye, associated with aging.
The default settings in aDesigner can be used independently. These are:
- crystalline lens transparency of 40 (years of age)
- and each of the three colour blindness
- protanopia
- deuteranopia
- tritanopia
aDesigner awards a maximum of 3 stars for each test. Pages can be deemed to have passed where they are awarded 3 stars on each of the 4 tests.
