Color Theory and Principles

The famous "RGB Color Cube"
11x11 (1331 points)
Black is the back corner
White is the front corner
Download Full-Size Color Cube
Color Wheel with Luminance
Black in on outside, White is in the Center
The Primary Colors are halfway inside the
circle - where the traditional Color Wheel colors lie


The Color Wheel / Primary Colors Myth - the traditional color wheel is technically wrong as are the primary colors that it defines !!  The color wheel is everywhere - and sadly, they are all wrong.  They all have show the 3 primary colors as:  Red, Yellow, and Blue.  In addition, many sources state that the 3 primary colors are Red, Yellow, and Blue.  But they are NOT !!  However, this is not technically true, or is at least inaccurate. The three primary colors of pigment are magenta, yellow, and cyan. (Thus when calling "red, yellow, and blue" the primary colors of pigment, "red" is an inaccurate way of saying "magenta" and "blue" is an inaccurate way of saying "cyan").

Color wheel

This all started in the Art world, where the colors red, yellow, and blue are considered to be primary pigments. They made the "Color Wheel", and millions were distributed, which solidified the myth.

A "perfect" set of paint colors is in fact magenta, yellow, and cyan - which, therefore should be the primary colors for paints. But of those 4 colors, only Yellow is a household word.  So they figured that magenta is very close to red .  .  .  and cyan is very close to blue. So heck - just use them instead.  Ever since that decision was made - we have been stuck with Red, Yellow, and Blue.  Here is the bogus color wheel that resulted and is now all over the world:


Our "RGB Eyes"

The back of the human eye, the "retina" contains thousands of tiny light sensors called "cones".  Just like the 3 colors *Red, Green, and Blue) that a TV uses to light the screen  .  .  .  there are 3 types of cones in the eye - red, green, and blue.   The cones are not narrow banded - in other words, they see all the adjacent shades and hues also.

Thus, for humans, mixing various amounts of three colors of light (red, green and blue) will produce all colors that can be perceived. Our vision see colors as additive" ! !  This means the light from each color component is added together to form the resultant color.

The eye "interpolates" colors depending which of the three cones are receiving light.   For example, there are two ways to make "yellow" light appear to the eye.

1) use equal amounts of red and green light. These stimulate the red and green cones, and the brain sees "yellow".

2) use the "Yellow" wavelength of light - which is between red and green (about 565nm). Because the response of the red and green cones overlaps, this single color also stimulates both the red and green cones.

The brain sees "yellow in both cases.

Primary Colors (the "real" primary colors)

A primary color must meet two criteria:

There are numerous color spaces, but you are likley to only deal with two of them - and each has its own primary colors :

  1. RGB color space (Red Green Blue) - has additive primaries.  Light - such as colored LED's, TV screens, computer monitors, etc - the colors are "additive" and the primary colors are Red, Green, and Blue

  2. CMYK or just CMY color space (Cyan Magenta Yellow blacK) - which has subtractive primaries  The letter "K" is from printing, where the "key plate" was use to print the color black.  Pigment - such as inks - the colors are "subtractive" and the primary colors are Magenta, Yellow, and Cyan.  The K is sometimes omitted and this color space is often called CMY.

is more than one "color space" - so the  in the gamut of a given color space. Primary colors may themselves be mixed to produce most of the colors in a given color space: mixing two primary colors produces what is generally called a secondary color, mixing a secondary with a primary produces what is sometimes called a tertiary color. Traditionally, the colors red, yellow, and blue are considered to be primary pigments in the art world. However, this is not technically true, or is at least inaccurate. The three primary colors of pigment are magenta, yellow, and cyan. (Thus when calling "red, yellow, and blue" the primary colors of pigment, "red" is an inaccurate way of saying "magenta" and "blue" is an inaccurate way of saying "cyan"). Blue and green are actually secondary pigments, but they are primary colors of light, along with red. If the color space is considered as a vector space, the primary colors can be regarded as a set of basis vectors for that space.

Primary, Secondary, and Tertiary Colors

Mixing two primary colors produces what is generally called a secondary color, mixing a secondary with a primary produces what is sometimes called a tertiary color. We can best show this using the tradition color wheel (yes, it is wrong - but it shows this concept well):

Traditional Color Wheel
- with its wrong RYB Primaries -


Additive (RGB, Light Colors) and Subtractive (CMY, Ink colors)

An additive color space (light) is one where colors will merge together and combine their wavelengths into a new color.  This is what colored light is - additive colors.

A subtractive color space  (paints and inks) is one where the pigment actually blocks, or "subtracts out" certain colors.  The color or colors that it does not block are reflected back out to our eyes and that is the color we see.  A banana is not really "yellow" - it blocks or absorbs magenta and cyan, and leaves only the yellow light wavelengths.  In essence, the banana subtracts all light frequencies out except yellow.

The colors of paint and crayons do not add color to the light we see; they absorb light from it.

Magenta paint will remove green from white light, reflecting back red and blue. Yellow removes blue light, reflecting back red and green. Cyan absorbs red, reflecting green and blue. If you combine cyan and yellow paint, red and blue are absorbed. In white light, this reflects only green. This is why blending blue and yellow paint gives you green.

We need to at least go over the theory of the "color wheel", "primary colors", and "complementary colors" to be able to explain printer inks.  "Primary Colors are described differently depending on whether it is a additive color (mixing light) or a subtractive color (mixing inks).

Additive color

 (used by Monitors and TV's) - mixing of colors of light, with the three primary colors Red, Green, and Blue.  The 3 primaries combined fully will result in white.

The image below shows how the light from red, green and blue flashlights would appear if shone on a dark wall. The three primaries in light are red, blue, and green. When all of the colors of the spectrum are combined, they add up to white light.  This can be shown in photoshop by using a black background, with 3 layers on top - where each layer is in "screen" mode so that the color is combined in an additive fashion with the colors below:

Additive Colors - RGB (Red Green Blue) Circles

*** the overlapping areas from RGB gives 3 of the Primary colors from the CMYK color space (Cyan, Magenta, and Yellow)


Subtractive color

 Used by Printers - which mix of colors of pigment with inks of the 3 primary colors Yellow, Cyan, and Magenta. When learning basic color theory, painting students typically use the color wheel (see the "myth") colors of red, yellow, and blue. But the techno world of printers did not buy into the myth, and they correctly use the yellow, cyan, and magenta for the primaries.  The example below illustrates subtractive color by showing how primary colors mix on a piece of white paper.  The 3 primaries combined fully will result in Black.

Subtractive Colors - YMC (Yellow Magenta Cyan) Circles

*** the overlapping areas from CMYK gives the 3 Primary colors from the RGB color space (Red, Green, and Blue)


Color Wheels

Color wheels show how visible colors are related. Primary, secondary, and intermediate colors are organized on a circular chart.  Color wheels are based on color theory, which is based on the physics of light. There are two common types of color: additive color and subtractive color.


Painters Color Wheel
the "standard color wheel"
Subtractive, with RYB primaries (which is "wrong")
dual color space wheel
RGB Additive and CMY subtractive Color Wheel
perfect !!!


Traditional (wrong) Color Wheels

** the one that is wrong (see "the Myth" at the top of this page)

Color wheels help artists remember how to mix and think about pigments. This is why almost all color wheels you see are subtractive wheels.


Color wheel
Color wheel with wrong primary
and secondary colors
Color wheel
Color wheel with wrong primary,
secondary, and tertiary colors

Subtractive "traditional" Color Wheels

- remember . . . traditional color wheels have the primary colors wrong !!
They show Red, Yellow, Blue for primaries instead of the correct Magenta, Yellow, and Cyan


Modern Color Wheels

Additive color wheels

the absence of light is darkness, add light to it

red + green = yellow green + blue = cyan blue + red = magenta

RGB (additive color) pairs add up to equal CMY colors


additive color mixing

The additive color wheel
red  +  green  =  yellow
green  +  blue  =  cyan
blue  +  red  =  magenta
red + green + blue  =  white

Additive Colors



subtractive color mixing

The subtractive color wheel
cyan  +  magenta  =  blue
magenta  +  yellow  =  red
yellow  +  cyan  =  green
cyan + magenta + yellow  =  black

Subtractive Colors

NOTE:  subtractive primary color pairs also add up to equal additive Primary colors


Hue, Saturation and Brightness

RGB (Red, Green, Blue) and CMYK (Cyan, Magenta, Yellow, Black) are other common color models. CRT monitors use the former, creating color by causing red, green, and blue phosphors to glow; this system is called additive color. Mixing different amounts of each of the red, green or blue, creates different colors, and each can be measured from 0 to 255. If all red, green and blue are set to 0, the color is black, is all are set to 255, the color is white.

The human eye can distinguish around a million colors, the precise number depending on the individual observer and viewing conditions. Color devices create colors in different ways, resulting in different color gamuts.

Color can be described conceptually by a three-dimensional HSB model: