The British Health & Safety Executive (HSE) has published an guide on "Colour
vision examination - employers' guidance".
Colour vision defects can be inherited or acquired during one's lifetime as the
result of diseases such as long-standing diabetes, cardiovascular disturbances,
multiple sclerosis, liver diseases and almost all eye diseases.
In the workplace, if an employer has employees with duties where colour vision
is important for safety critical purposes then colour vision testing is crucial
in determining fitness for work. However, in companies where colour vision
needs are not associated with safety-critical systems but with product quality,
colour vision testing is valuable to avoid costly errors.
When considering safety, colour is used in a number of ways, eg identifying the
most appropriate resistor (an electrical component) to use from the different
bands of colour on the resistor, or cylinders and pipes which may have part of
their bodies colour coded to indicate their content. Where safety depends
entirely on the correct recognition of a colour code, for example in some
electrical and electronic engineering work, and in some transport applications
(eg train driver), normal colour vision will be required. There are some jobs
though where safety considerations are minimal but quality control requires the
correct identification of colours, eg in industries such as textiles, paper
manufacture, dyes and paints.
A person with a colour vision defect perceives a wide range of different
colours as being the same, which to a colour-normal person appear to be
different. The colour confusions are variable and can be mild, moderate or
severe. In some cases, individuals are not aware of their defective colour
vision until errors are made.
A whole range of defects are found in practice. While some people confuse
bright colours, others may only have problems with pale colours exacerbated if
the level of illumination is low. Colour confusions can also occur when tasks
involving small areas of colour are present, or where larger areas are viewed
at a distance.
AplusA-online.de - Source: Health & Safety Executive