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A bit of physics and Biology: The 3 characteristics of color


If we see an object, it is thanks to the light which leaves from this object and reaches our eye. Without light, we see nothing. This light can be emitted by the object itself (this is the case of the filament of a bulb, the sun and the stars for example), or else reflected (the moon for example is visible only because it is lit by the sun, and most of the objects that surround our daily life do not emit light either, but we see them thanks to the light they reflect).

A light color has a greater brightness than a dark color. The brightness of a color therefore corresponds to the amount of white light reflected by that color. If all the white light is reflected, the object will be white, whereas if it does not reflect any light, it will be black. The difficulty in appreciating the luminosity of a color is to manage to disregard its saturation and its hue. Biologically, within our eye, the cells that are specialized in the perception of light are called rods.


The hue is governed by the dominant wavelength of the light received by our eye (therefore emitted or reflected by an object that we see). This wavelength is part of the visible spectrum (otherwise we just wouldn't see the object in question!).

It is the hue that allows us to distinguish a blue from a pink or a green. In our eye, cells called cones process this data. The cones of the human eye are more sensitive to wavelengths between green and yellow than to those at the end of the visible spectrum. Thus, the human eye discerns rather badly variations in color between blue and purple for example.

We call pure tint a tint that corresponds to only one wavelength. On the chromatic circle, we find these colors at the end of the circle. We then speak of saturated colors.


A saturated color is called monochromatic, because it consists of only one wavelength. Saturation therefore expresses the purity of a color. The less saturated the color, the further away from the periphery of the color wheel. To reduce the saturation of a color, just add white to it. Here again, it is also the cones which make it possible to appreciate the differences in saturation.

Brightness, hue, saturation: the graphic summary

The different color categories

Additive and subtractive syntheses

There are two ways to synthesize color. One applies to colors resulting from the emission of light (additive synthesis), the other applies to those resulting from reflected light (subtractive synthesis).

Additive synthesis: Let's imagine us in a play, unlit. The show begins: the spotlights come on, each adding a different color (wavelength). By lighting the same point on the stage with all these spots, the more the stage manager lights, the more the point lit on the stage will be white. Light = Additive.

Subtractive synthesis: Now let's imagine that we are about to print a poster on paper. This time, the background is not black as in the theater, but white. Each color you add will remove white from that paper, and the less white, the lower the brightness of the color. By adding all the colors on the same point, we manage to make the white completely disappear, and the color obtained is none other than black. Painting = Subtractive.

So, in your opinion, do the colors on your computer respond to additive or subtractive synthesis? (answer below!)

Primary colors

There are three of them, and they differ depending on whether we are in additive or subtractive synthesis. Specifically, additive primary colors are opposed to subtractive primary colors. The three primary colors are chosen in such a way that once superimposed on each other they give white or black (depending on whether it is additive or subtractive synthesis). For subtractive synthesis, the three primary colors are Cyan, Magenta and Yellow (CMY), while in additive synthesis they are Red, Green and Blue (RGB).

When you work on a computer, each pixel emits a color. When the pixel values ​​are at 0, the screen is black, conversely when they reach the maximum values ​​the screen is white. You are therefore in additive synthesis!

In the rest of the presentation of colors (secondary then tertiary) we will limit ourselves to additive synthesis (RGB), since you are probably reading this article from a bright screen.

Secondary colors

The secondary colors are obtained by the mixture of two primary colors, quite simply. In additive synthesis, the secondary colors are therefore Cyan, Yellow and Magenta. Do these three colors ring a bell? Normal, they correspond exactly to the three primary colors of the subtractive synthesis!

Be careful, unlike subtractive synthesis, in additive synthesis it is normal for the mixture of two colors to give a brighter color.

Tertiary colors

In an additive system, the term tertiary color can have several meanings. On the one hand, tertiary colors are obtained by mixing a primary color with a secondary color, in equal parts. They are therefore six in number, but their name in the additive system (unlike the subtractive system) is not defined. On the other hand can be considered as tertiary colors mixtures in equal parts of two secondary colors, and in this case there are three, supplemented by three quaternary colors.

Then there is the entire infinite spectrum of shades, changing the mixing ratios of each color.

Complementary colors

In additive synthesis, two colors are said to be complementary if, mixed together, give white. They say they "cancel each other out". They are easily identifiable on the color wheel because they are opposed to each other.

Warm and cold colors

The notions of hot and cold colors were born in 1728 with the publication of the Richardsons Treatise on Painting and Sculpture. Opinions sometimes differ on the exact colors belonging to the pole of warm shades and that of cold shades, but it is generally accepted that red-orange belongs to warm colors while blue-green belongs to cold colors. This distinction would derive from our observation of landscapes: daylight gives them a warm tint while, conversely, twilight or overcast weather gives them cold tints. This distinction would therefore emanate simply from the differences in luminosity.

The perception of hot and cold colors has evolved throughout history. Michel Pastoureau says that in the Middle Ages and the Renaissance, on the contrary, blue was considered a warm color. But whether hot or cold, blue and red are generally strongly compartmentalized. Also in the Middle Ages, the dyehouses that had the authorization to dye red could not dye blue and vice versa, and it was accepted that the red dyehouses also dealt with orange and white tones, while those of the blue took care of black. Note that under these conditions it is difficult to obtain green by simply mixing blue and yellow! (in subtractive synthesis this time). This is, among other things, what Michel Pastoureau talks about in his little book entitled Vert, and which I "warmly" recommend you to read!

Warming up a shade is therefore adding a warm color to it, while cooling a shade consists of adding a cool color.

Isophane colors

We call isophane colors colors having the same value, the same gray level. If the image were shades of gray, one simply could not distinguish two isophane colors, because only the hue distinguishes them. Such a choice of color can sometimes pose reading problems, and generally tend to flatten an image rather than give it depth.

Pastel colors

Pastel colors are low saturated and bright colors. These settings give colors that are qualified as soft, clear or even tender.

The different types of contrasts

Brightness contrast

This is the phenomenon that makes the same color appear darker when it is on a light background than when it is on a dark background. If you want to look tanned, dress in white! This difference in persception is due to the ability of our pupil to adapt to the brightness of an environment. In a bright environment, the pupil closes, letting in less light, making the color appear darker.

Saturation contrast

Also called "quality contrast", this contrast emerges on the juxtaposition of colors with different degrees of saturation. We commonly speak of bright colors for saturated colors and dull colors for those that are less saturated. A color put on a dull background will appear more vivid than put on a more saturated background because our eye evaluates the saturation of a color in relation to its environment.

Color contrast

The color contrasts can play on the juxtaposition of primary shades or warm and cold shades for example. Such a contrast gives an additional tint to a color: the same orange will appear more yellow on a red background and, on the contrary, more red on a young background.

Simultaneous color contrast

The simultaneous contrast of colors is the name of a law enunciated in 1839 by the French chemist Michel-Eugène Chevreul: "The tone of two areas of color appears more different when observed juxtaposed than when observed separately, on a common neutral background ". (The "tone" of which Michel-Eugène speaks here is none other than what is also called the hue). He also published in 1889 a work entitled The Law of Simultaneous Color Contrast.

Examples: the juxtaposition of an orange and a blue makes the orange brighter, the same for a red juxtaposed with a green or a yellow juxtaposed with a purple. The painters of the Impressionist movement, born some thirty years later, have largely exploited this law. Opposite is given as an example a painting by Claude Monet, Coquelicots, 1873, in which we can see this juxtaposition of red and green.

The juxtaposition of two complementary colors reinforces the perceived saturation for each of the two colors. This optical phenomenon is due to our perception of colors. When our eye perceives a color, it simultaneously "demands" its complementary color. It is this simultaneous perception of the complementary color to the one we are looking at that strengthens each of the two juxtaposed colors when they are precisely complementary. The juxtaposition of secondary or tertiary colors also gives the feeling of being more saturated.

Decoration professionals know it well: while certain contrasts allow a space to be enlarged by giving it more depth, others, on the contrary, tend to make it flattened. It is therefore not a choice to be made lightly!

Tools to facilitate the creation of harmonious color palettes

To help you create the most suitable color palettes for your job, style, desires, or study topics, let's take a look at some of the free tools you can use.

Create a color palette from an image

Canva offers 4 color palettes created from the image of your choice. Choose one that inspires you or that is in line with the subject you want to cover! You will then only have to copy the proposed colors. Click here to create your first palette on the Color Palette Generator de Canva ! Here the chosen image is a drawing of the talented Rohan Dahotre, wild life designer.

Create a color palette from chromatic harmony rules

Adobe has also developed its color palette creation tools allowing you to choose a certain type of graphic harmony (monochrome palette, complementary colors, etc.) but also of course to vary both the hue and the saturation. Once satisfied, all you have to do is save your entire palette. To discover Adobe Créateur de Palettes , it's over here!

Choose a color palette from predefined palettes

Coolors is a site offering ready-made palettes, ranging from a few colors to a dozen. It's a great tool for seeking inspiration! I'll let you browse through these palettes in the Catalogue de Coolors.

Take inspiration from the thousands of Pantone colors

The Pantone color catalog lists all Pantone references, and that's saying a lot because there are a lot of them! The ideal place to find unusual colors and find new inspirations. The liste des couleurs Pantone is over here!

And to find the name of a color, you have to go to the Color Finder !

So what color palettes have you created? Join Beink sur Instagram and share your most beautiful palettes!

References :


- La Méthode Physique

- Thèse Soustractive Objectifs

- Physique et Chimie

- Hisour

- Les Yeux d'Argus

- Wikipédia: l'Impressionnisme

- CRDP de Poitou-Charente

- Danielle's Graphic Art