In this section, vision, touch and hearing are considered in turn, as the most commonly used senses for giving information. Practical hints are given which should give an idea of how to approach design with visually impaired people in mind. Remember that people need information about the current state of an item, for example, the time shown on a clock and whether or not the alarm is set. They also need to know what settings they have selected, for example, what time the alarm on the clock is set for. When making equipment accessible for Vl people, it is important to give only the information that they need, as superfluous decoration confuses.
Good displays have large differences in both.
Tone is best understood by imagining what something would look like on a black and white photograph. For example, bright red and blue contrast greatly in terms of colour, but very little in tone. A difference in tone is usually more important than a colour difference. Yellow seems to be a particularly easy colour to see and is often the last to be 'lost'. It stands out in many situations, especially against black.