I have read much about what is written about colour, and have found some interesting ideas that are worthy for elaboration and clarification. Below is an shorter adaptation of some of my own notes and small essays on colour. This has been slightly updated for relevance to astronomy and double stars.


One of the most interesting aspects is on the perception colour and the alleged differences between the sexes. Much of this has been generated by the unfounded fable that somehow women have some kind of superior vision and colour perception. The modern scientific view has shown there are no significant physical or genetic differences between human males and females in interpreting colour. Most of the current literature also still confirms this view. Recently, colour scientists have shown that the main differences in colour perception between males and females is psychological rather than physiological ones.

The reasoning follows that for women their mothers, and female peers, from an early age train their daughters and young girls in colour perception and colour matching, especially after puberty. Subjects are deemed to have improved perception, being merely based on their vastly larger and better colour vocabulary and knowledge.

Important examples are in colours seen nylon stockings, lipsticks and fabric colours displayed under fashion parade lighting. Naturally women, who typically are faced with applying face make-up will soon learn the subtleties of colour. Often this involves matching of cosmetics to achieve the desirable effects they want. This is also shown in the comparison or matching of many additional fashion accessories, such as shoes and handbags with their own clothing.

Men in life are generally not faced with any degree of colour matching, and psychologically often do not need or use such colour terminology. Others in this field of study say the biological need for women having the colour knowledge is to improve their attractiveness to their male counterparts. Some have said that certain colours, like red, are more noticeable by males. I.e. Males more often see red on females rather than on other males. Psychologists technically called this a distractor, being basically a female lure searching for a suitable mate and probably the reason why red is perceived as a warm and vibrant colour. Promotion of blood-red lipsticks or rouge by the cosmetic companies, for example, heightens the fullness of the lips and cheeks. This suggests they are fertile and are seeking suitably healthy sexually partners. Red in our society also symbolises aggression and violence. This colour can appears as a natural flush on the face, especially on the cheeks and lips. When someone is angry or has undergone extensive physical activity. This physical response is the warning to others, suggesting they are in a more aggressive mood and are ready to fight or defend themselves. Red colours also often indicates having higher blood pressure, and the likelihood of increase in the hormone, adrenalin. Additionally, in male cases, the prominent male hormone, testosterone. Our response to the colour red is exploited, such as red flashing warning alarms or red traffic lights to stop vehicles thoroughfare. Even most police cars have red and blue flashing lights — the blue enhancing the intensity of the already prominent red warning.

There are many examples of using colour to reflect mood, and this is more likely derives from environmental differences. As yet, no physiological difference has ever been found to influence either the rods and cones of the retina to account for this. Colour may affect the individuals emotional state, however, the observed effects are mainly influencing brain chemistry and the interaction of with various organic compounds including for the hormone and adrenalin release into the blood stream. Some recent studies on the nature of these mechanisms towards our understanding on this subject remains quite incomplete.

For our discussion here, the basis of the physiological chemical mechanism for all human eyes — male and female — is having the main chemical pigment known as 11-cis Retinal. This is available in the principle photoreceptors and is a photosensitive chemical component — working not too unlike the silver halide crystals used in black and white photography, that measure the light intensity. The 11-cis Retinal in the reaction combines with specific proteins, called amino acid glutamates, which then become the colour chemical interpreters for the photoreceptors. The human brain has acquired by evolution these latter proteins for colour discrimination and is some cases the erroneous recombination of the wrong interpretation of colour producing various colour defects.


The main problem with colour perception between the sexes is with the genetic defect known as colour blindness. It has been found that the so-called anomalous trichromacy affects some 6% of colour vision in men, meaning they are unable to properly discriminate the colours displaying reds and greens. Another 2% are so-called dichromats, and are deficient in the pigments needed for discrimination of both long and middle wavelengths. Men are also ten times more likely to have some form of colour blindness defects than women. Most colour blindness is caused by the known defect in one specific gene that causes lack of eye sensitivity by either the red or green cones, properly termed as protanopia. Another is the much less frequently diagnosed blue cone defect known as deuteranopia.

Overall, visual colour problems are often caused by the incorrect usage of the chemical pigments. In simpler terms, it works like CRT televisions, where one colour gun is working incorrectly and not targeting properly, or even has one gun is not functioning at all. I.e. Take out the red component so the colours that are seen are mainly yellows, blues and greens, etc.

Total Colour Blindness occurs in 1:40,000 individuals, equally between men and women, where the cones do not form from birth. Such persons are sensitive to high intensity light and have vision that is akin to your surrounds as they appear during normal vision in twilight, and of course, naturally with perceiving any colour. Sometime other individuals have no rods all, and have to rely solely on their cone vision. These individuals are completely night-blind, being medically diagnosed as hemeralopes.

Another more general fault is that the spectral range of the visual wavelengths narrows with age. Physiological causes for this problem is more likely because the rods and cones are slowly reducing in total numbers. This might be further combined with increasing inefficiencies of the chemical signals being sent to the brain along the neural pathways.

Although the visible impact is usually only minute. During the daylight hours there is always overwhelmingly sufficient amount of light. Hence the general effects become far more pronounced only because less photons are available to detect colours or intensity of starlight. I.e. If colour degradation were, say, 25% for example, and that some one million photons were received in one second of time during daylight hours, then the loss of light would be of little consequence as there is already enough light available for colour discrimination. Yet if one hundred photons were received over the same period the overall effect would be more dramatic and obvious. To our eyes, this manifests as the gradual loss colour perception, so that the sky would becomes more greyish. (Note that if this postulate is true, this would mean have slightly more trouble discerning bright nebulosities in the telescope as we grow older.)

A secondary effect is that the range of observed colours also diminishes. Here the ability to see blues and reds, for example, at either end of the visible spectrum becomes harder and harder to see. As our eyes are not as sensitive to reds, then you should also find that the perceived blues intensity gradually gets slightly lesser over time. This combined with the decreasing light intensity will find that colours become less obvious to the individual. I suspect that the age where these effects start happens at the average age of about fifty-years old, though the actual age might varies between populations over several decades. (See Figure 6.)

Colour Contrast

Figure 6. Colour Loss With Age

Figure 6 shows the expected explanation for most of the loss of colour vision as we age. Although arguably subjective, it does explain what is happening regarding the general discussions about colour perception with people of various ages. Importantly, some people may never experience any loss of colour at all, while others may find these changes and differences sudden and quite dramatic. Again there is no real better or worst in this situation and certainly no superior colour vision. Those who claim otherwise are being misleading or are probably trying to justify their point of view.


Still unexplained in nature is why colour-vision in humans are similar between the sexes, but is much more different than the many other colour-visioned mammals. I.e. Apes and monkeys have known significant differences in colour perception between males and females. Typically, these primates have males with two types of colour cones dichromats while the females do have three different colour cones or trichromats. The postulated reason for this has been something to do with either behaviour modification or being necessary for mate selection. [Some religious discussions have used these particular facts against Charles Darwins Theory of Evolution.]

Note: Only 2% of all human males are dichromats — being probably the genetic eye defects from misaligned X-chromosomes (in the sex determining XY pair) that are responsible for vision.

The chemical proteins for the coloured-cone photo-receptors are attached to the XX and XY. Interestingly women do have the duplication of these cone receptors while males do not. This easily explains the increased number of males that have imperfect genetically colour vision. However this does NOT mean that females have, as some submissions I have read have claimed, of better or improved vision, as the chemical and physical mechanisms are just exactly the same. In evolutionary terms, our eyesight maybe one of the earliest to develop especially as keenness of sight has definite advantages for hunting of animals or spear fishing fish for our sustenance.

Colour genetic defects in women may mean they can be so-called tetrachromatic, which are likely women who have had sons who are dichromats. (Jordan, G, Mollon, J.D. A study of women heterozygous for colour deficiencies., Vision Research, 33, 1495-1508 (1993)) Here, they mismatch the colours, and they have slightly better capabilities in separating red to orange colours. However, such women are literally one-in-a-million.

For a continuance of this page:
See Star Colours 5. (Next)


Last Update : 29th August 2014

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