Small Color Inventory and Classification¶

Perceived colors are therefore blends of monochromatic* light rays. Let’s see how to classify all these colors and how they are decomposed.

Black¶

The simplest color is therefore black*: total absence of light is perceived as black. When the light intensity decreases, colors gradually approach black. But when the intensity rises, colors don’t whiten! The higher the intensity, the more the color appears “bright” and “saturated”, but doesn’t fade, doesn’t whiten ¹.

Monochromatic lights¶

The simplest colors, and the rarest (they’re those emitted by Lasers for example), are those composed of a single monochromatic light. They’re in fact the colors of the rainbow, those which are included in the monochromatic spectrum.

They range from red to blue, through orange, yellow, green, cyan… but don’t include any shades of purple*.

They can vary in intensity, in a scale from black (null intensity) to the “brightest” color.

Purple¶

It should be noted that the purple/violet range² isn’t part of the “natural” and monochromatic colors but is the result of the blend of blue and red rays, which are the two extremes of the spectrum.

Purples added to the monochromatic colors form the set of the most saturated* colors, which are therefore all monochromatic colors and blends containing only blue and red.

White and Grey¶

In nature, all lights, or more precisely all light rays, are monochromatic*; it’s the perception of their blending that’s interpreted by the brain as an infinity of other colors. We saw that purples are part of these blends; all the other colors which aren’t saturated*, grays and whites, are therefore also mixed lights.

All “desaturated” shades, whites, grays, are blends of these monochromatic colors, and there is for each color (and not only grays, all non-monochromatic colors) an infinity of different blends which can generate it.

Two colors perceived in an identical way but composed of monochromatic rays in different proportions are said metamers*.

Complementary colors¶

A minimum of two “opposite” rays is needed to form white: two monochromatic rays that form grey/white when they’re blended are said to be complementary*.

Purples can also be considered complementary to greens. Indeed, a purple blended with green becomes white³, and can therefore be considered as the complementary of green⁴, although it’s actually already the combination of red and blue. These green, red and blue are the three common primaries of digital color reproduction systems.

Perception¶

The same white sheet of paper will be seen as white regardless of the time of day or the type of lighting, although in reality its color is quite different in each of these cases: the sheet of paper will in fact take on the color of the light that illuminates it, but the brain will operate a “shift” in perception that will make it appear white in all cases.

Under the sun, in the shade or surrounded by the clouds, whatever the time of day, we perceive snow as white even if in reality the light it reflects is always time different⁵.

different sets of light rays, with completely different physical attributes, can be seen the same way by a single observer. The perception of colors is eminently subjective.