by Petrônio Bendito

Perceptual Notation System

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Updated RGB|CMY Color Wheel by Petronio Bendito

Bendito's Master thesis 'Perceptual Analysis of the RGB Color Cube' has led to the development of a perceptual notation system. This notation has been greatly influenced by the works of Munsell, Birren, and Ostwald.

earlier RGB Color Wheel

The RGB3 Color Wheel

The RGB3 Color Wheel is made up of three primary colors:

Red, Blue, and Green.

There are three secondary colors on the wheel that are produced when primary colors are mixed:

Blue and Red mixed create Magenta.
Red and Green create Yellow.
Green and Blue create Cyan.

The transition steps in between the primary and secondary colors are what make up the tertiary colors and are named as follow:

Red-Yellow, Yellow-Green, Green-Cyan, Blue-Magenta, Magenta-Red.

Each tertiary color is divided into four sub-categories as seen in the color wheel.

Example: Cg, CG, GC, Gc.


Notation Structure

The primary and secondary colors are represented by the beginning letter of their name:

R = Red
B = Blue
G = Green
M = Magenta
C = Cyan
Y = Yellow

Tertiary colors are made from a combination of primary and secondary colors. The notation for the tertiary color is the combination of the two beginning letters of the colors they are made of. For example, Red (R) and Yellow (Y) produces the tertiary Red-Yellow.

The Red-Yellow is subdivided into five color steps which are labeled Ry, RY, RY, YR, Yr. The upper and lowercase letter are used to represent the level of perceptual predominance of either a primary or secondary color. The capital letter indicates the predominant color:

Ry = Mostly red, a little yellow
RY = Almost even, more red
RY = Even amount of red and yellow
YR = Almost even, more yellow
Yr = Mostly yellow, a little red

Note: The RY colors do not appear in the RGB3 Color Wheel.


Expanded RGB3 Notation System

The colors of the RGB color cube can be mapped within consistent patterns related to a gray scale and to the level of purity of the color as shown below:

The RGB3 gray scale has 6 even steps from black to white. The intensity of a color increases from left to right towards its pure state.

Each color can be mapped according to the family it belongs to (i.e. red, blue...), its relation to the gray scale, and its level of intensity.

For example the notation Y 8/4 means:

  • Y = This color is yellow (Y)
  • 8 = This is the location of this color in relation to the gray scale.
  • 4 = This is the level of intensity. Color has low intensity.

Similarly the notation Y 5/10 means:

  • Y = This color is yellow (Y)
  • 5 = This is the location of this color in relation to the gray scale.
  • 10 = This is the level of intensity. Color has high intensity.

The illustration below provides a visual summary of
the RGB3 Perceptual Notation System:

Note: Compare the three notation system below. The perceptual notation (PN) system has the potential to pinpoint the color family, its relationship to the gray scale, and its level of purity (intensity):

Y 8/4

R= 255
G= 255
B= 153

Y 5/10
R= 255
G= 255
B= 000


PN Notation Limitations
This notation system has been applied only to the web color lookup table (also known as the web safe colors) which is composed of 216 colors sampled from the RGB Color Cube.


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[This page was archived on December 10, 2014] Copyright © 2001. P. Bendito. All rights reserved.