Secular scientists would argue that our ability to perceive color evolved because it has survival advantage.  Of course, the irreducible complexity of our visual system argues against any evolutionary origin.   All the essential parts of the eye must already function properly in order for the eye to be of any value. 

Our eyes and brain provide us with a nearly instantaneous mental picture of our immediate surroundings.  This in itself is amazing and should prompt us to thank and worship our Creator.  But the Lord has enhanced our visual experience with a wonderful feature: color.  What exactly is color, and how do our eyes and brain process it?

Color

People tend to think of color as a physical property of a substance or of light.  But it really isn’t.  Color is a mental experience.  Particles of light do not literally have color, nor do physical substances.  The only place color truly exists is in the mind.  But then how do we make sense of statements like “grass is green” and “the sky is blue?”   What we really mean by this is that grass absorbs certain wavelengths of light and reflects others, such that when those wavelengths strike our retina, they are processed into signals that our brain interprets as “green.”  But the photons (the particles of light) do not have color, and under the right circumstances those same photons (combined with others) can produce a different mental experience (such as “white”).  So how does this work?

In previous articles, we explored the retina – the dark, internal, light-sensing surface of the eye.  The retina contains light-sensitive cells called rods and cones.  The cones are what allow us to experience color.  In healthy human eyes, there are three types of cones.  Each type is filled with a unique photopsin – a light-sensitive chemical.  The L-cones are filled with a photopsin that is maximally sensitive to long wavelengths of light (hence “L” for “long”), with peak sensitivity to light of 564 nanometers.  The M-cones are filled with a photopsin that is maximally sensitive to medium wavelength light with peak detection at 534 nanometers.  The S-cones are most sensitive to short wavelengths of light, with peak sensitivity at 420 nanometers.

In fact, all three cones can detect a range of wavelengths.  But the signal they send will be strongest if the wavelength of the light is near their peak sensitivity.  In other words, even the L-cone can detect short wavelengths light, but it produces a much weaker signal than the S-cone does for short wavelengths.  Most of the light that enters our eyes is comprised of many different wavelengths.  But if a majority of those wavelengths are long, the signal from the L-cones is strongest and we perceive the color red.  Conversely, if the majority of wavelengths are short, the S-cone response is strongest and we perceive blue, or violet.  A majority of medium wavelengths with an absence of short or long produces the sensation of green.  If all wavelengths are present in roughly the same proportions, we perceive white.[1]

Interestingly, the majority of our cones are L-cones, with M-cones being the second most common.  The ratio of M-cones to L-cones varies from person to person.  However, only about 2% are S-cones.  This means that our visual acuity is highest for longer wavelengths, and lowest for short wavelengths.  So, a distant illuminated sign that appears red will be easier to read than one that is blue – all other factors being equal.

3D Color Space

All colors that we are capable of perceiving are due to the relative contributions of the L, M, and S cones.  For this reason, it is possible to produce any color experience by combining three different wavelengths of light in the right proportions.  Televisions and computer monitors make use of this principle.  A standard television produces our color experience by combining light from three color elements – red, green, and blue (the colors we would perceive if the elements were viewed in isolation).  Our vision is therefore referred to as trichromatic vision.  For a trichromat, any color can be produced by combining light from three other colors.  This makes sense because we have three different types of cones, each sensitive to a particular color range.  The possible combinations are such that a human being with healthy eyesight can discern over 10 million colors!

A trichromat has a 3-dimensional color space.  That is, every possible color can be produced by combining only three primary colors in the right proportions.  We might refer to light that produces a “red” experience when viewed in isolation as “red light.”  If we then add red light to green light in roughly equal proportions then you will see yellow light.  Add yellow light to an equal amount of blue light and you will see white light.[2]  So, you can perceive “white” by combining light with only three different wavelengths in the right proportions.  On the other hand, you will also perceive “white” if you combine all visible wavelengths of light in equal proportions.  You cannot tell if a given “white light” is made of just three primary wavelengths of light, or all of them.

Most mammals are dichromats.  They have only two types of cones, and therefore all colors they can experience can be produced by combining only two different wavelengths of light – a 2-dimensional color space.  But human beings have a richer color experience due to that third cone.  Some animals have more than three types of cones.  Finches, for example, are tetrachromats – having four types of cones.  Some animals have even more.  The mantis shrimp has 12 types of cones![3]  There are reports that some human beings have tetrachromatic vision due to the addition of a fourth type of cone – but it is rare.  More commonly, some people are missing one of the three types of photopsins due to a mutation, resulting in dichromatic vision.

The Fall

Since the fall of man, many things no longer work perfectly in this world.  Human color perception is also subject to the fall, and problems can manifest in a number of ways.  A rare defect can cause the cones to fail to develop properly, resulting in total color blindness along with a substantial reduction in visual acuity.

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