In order to be accessible
to users with visual acuity limitations, an interface displayed on
any device must have a sufficient degree of contrast between the
background and the foreground (e.g. text) [2] [10]. High contrast
makes UIs more discernible for the many older adults who
experience greater difficulties distinguishing between colors with
a low level of luminance contrast, due to age-related changes [21].
When designing for older adults, UI elements should be highly
contrasting, using negative (light text on dark background) or
positive (dark text on light background) polarities. Although
the two polarities have similar levels of readability, it has been
argued that the negative polarity is slightly easier to read on
the screen [25].
The Health Channel uses a negative high contrast color scheme
throughout the UI. Throughout evaluation of the working system,
participants were able to read and comprehend the display without
visible or stated difficulty.