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John Dalton was a famous chemist in the 18th Century. Yet, he was a man who described blood as bottle green, and considered a laurel leaf as a good match for red sealing wax. Fortunately, others in his field recognised that Dalton was suffering from color blindness, or, more correctly, defective color vision. Dalton became so well known with his faulty applications of color in his work that in some parts of the world color blindness is referred to as Daltonism.

About 1 in 20 people are affected by color blindness. So, why do they see color differently than others? Well, a person sees normal colors if three beams of light, red, green and blue, are combined in equal proportion to produce white light. When those three beams of light are combined in unequal proportions, other hues of color are produced. Yet, a color blind person is only able to mix two of the primary colors. Such a person is known as a dichromat, being defective in one of the primary colors. For example, a person may be a green blind dichromat. A more serious condition is that affecting monochromats. These people have no color discrimination at all. For them, life is seen in black and white. The majority of those affected by color blindness, however, are what are known as anomalous trichromats. These people are still able to see hues produced from the three primary colors, but the proportions that they see are distorted.

Why do these people see things differently? It comes down to light receptors, or cones, of which there are about 130 million. About 7 million of these are applied to our color vision. There are three types of cones that operate in people with normal color vision: those that respond best to long wavelengths of light (bue), those that respond to middle wavelengths (green) and those that respond to short wavelengths (yellow). Damage to the optic nerve that affects the cones' message to the brain can cause color blindness. It has been shown that certain chemicals and stimulants, such as alcohol, tobacco and oral contraceptives can also affect color vision. The aging process can also affect color perception, especially with regard to blue light. Most colorblind people however, are born with the defect.

Color blindness is a sex linked genetic disorder, transmitted by females but usually appearing in alternate generations of males. If you are born color-blind, then, it is likely that your grandfather had the same condition.

If you suffer from color blindness here are some precautions that you should be aware of:
(1) Rather than relying on color to make decisions, be more aware of the shape, brightness, position and shape of items.
(2) Be realistic about how, if at all, your defective color blindness will affect your work. Don't ignore the condition in an attempt to secure employment, as it will catch up with you in the end.
(3) Avoid excessive use of alcohol or tobacco, as this will further deteriorate your already faulty vision.
(4) Let your associates know that you are affected by defective color vision.

Color blind people are at a slight disadvantage in the use of the eye, that amazing multi-functional camera in our heads. Yet, they are still able to utilise many of the other abilities of sight. Keeping in mind the common sense suggestions above, they will be able to utilise the ability of their eyes to it's full, though limited, potential.