Five to ten percent of all people have a deficiency in color vision
known as “color blindness”. Most people can see colors to some
degree, but not all people see colors in the same way. For example,
people with Protan vision have difficulty seeing red, people with
Deutan vision have difficulty seeing green, and people with Tritan
vision have difficulty seeing blue. Avoid using certain color
combinations in critical applications, because not all people can
distinguish them. For such color blind users, you must use what is
known as “color picking”, which is the
deliberate avoidance of colors that color blind users are unable to
distinguish. Specifically, when you use a set of colors in a
diagram or chart, you should avoid using red and green in the same
display for red-green-blind users, but you can use a range of
colors from blue to yellow. The same applies to using blue and
yellow in displays for blue-yellow-blind users.
In accessible applications, the information that is presented by
using colors is also presented in other ways. The colors that are
used therefore become redundant and are known as “redundant colors”. For example, the data
presented in a diagram or chart might be presented additionally as
text in a table. Graphic objects might be presented additionally as
specific shapes, or with alternative color schemes, so that colors
are not the only way to distinguish items.
You can find a sample that illustrates the accessibility features
of the JViews Framework
in <installdir>/jviews-frameworkxx/samples/accessibility.