What colors are considered primary colors?

Answer 1

There are quite a few different colors that can be considered primary colors.

Since human eyes sense color with cone cells, and human eyes have only 3 kinds of cone cells, 3 primary colors suffice to produce every possible hue (but not every possible color).

Question: what is meant by "every possible hue (but not every possible colour)"?

Fact: Simple primary colours - of any triad (red-green-blue or cyan-yellow-magenta) - can not produce supersaturated fluorescent colours. Colour television and colour printing are therefore limited to a restricted range of colours - look up the CIE Chromaticity Chart to discover the full gamut of "television" colour.

Painters *can* produce a wider range of colours, as their red and blue pigments can be more "red" or more "blue" than the pigments used in television or painting. FOur-colour television adds a yellow phosphor/pigment that cannot be produced by three-colour systems, and thus it gives more vibrant yellows.

Subtractive ink primaries

"Full-color" printers use cyan, magenta, yellow, and black inks (CMYK) in their printing presses -- therefore full-color printing is often called 4-color printing.

The cyan, magenta, and yellow can be considered the 3 primary colors, sufficient to produce every possible hue.

C + M + Y = in principle, black, but in practice it often results in a dark brown color -- so in practice, printers produce black on paper by directly using black ink, which also saves on ink and reduces drying time.

C + M = blue

M + Y = red

C + Y = green

no ink = white paper.

Additive primaries

The additive primaries are red, green, and blue (RGB).

By selectively combining red light, green light, and blue light, one can produce a wide range of colors, including every possible hue.

All full-color televisions and Computer Monitors produce varying amounts of red, blue, and green light at each pixel. (The "green" light is often called "lime").

red + green + blue = white

red + green = yellow

green + blue = cyan (more or less the same as aqua)

red + blue = magenta (more or less the same as purple, violet, fuschia, etc.)

lots of red + a little green = orange

all off = black

Painter's primaries

Many painters have 3 or 4 tubes of paint squirted on the palette used as "primary colors", in the sense that every bit of paint that ends up on the painting is one or the other of those paints, or some mixture of them (possibly also mixed with pure white or pure black paint or both).

But the particular colors chosen vary from one painter to another.

red, blue, and yellow

Some painters say that

Red, blue, and yellow are the primary, or basic, colors.

These painters place these "primary" colors equally spaced around a color wheel.

Many painters often use a traditional color wheel with the "secondary" colors violet, orange, and green placed between the primary colors, in the order: red orange yellow green blue violet (ROY G. BiV).

It is not possible to produce green with only red, yellow, and blue (even if one adds black or white or both).

There are 3 ways to work around this green problem:

CMYK (again)

A few painters use "process blue", "process red", "process yellow", and black -- which are exactly the same cyan, magenta, yellow, and black used in CMYK printing.

red, blue, yellow, and green

Other painters using the opponent process color theory use colors sometimes called the "psychological primary colors", one at each end of 3 opposing channels: red vs green, yellow vs blue, and black vs white.

These six "elementary colors" are often used for children's toys.

4 or more colors

While 3 saturated colors are sufficient to access any hue,

any mixture of colors produces colors that are not fully saturated.

Many painters use 4 tubes of saturated colors (not necessarily the same ones as the "psychological primary colors") or 5 or more tubes of saturated colors in order to produce colors that are impossible to access (i.e., they are more saturated) than in any system limited to only 3 primary colors.