1. What is Color?
Color is related to the wavelength of light. If a color corresponds to one particular wavelength, this is called a spectral color.
=600 nm corresponds to a color, but naming it is not an exact science….
orange chrome, golden poppy, spectrum orange, bitter sweet orange, oriental read, Saturn red, cadmium red orange, red orange…

2. Newton’s Study of Colors
Plague hit London in 1665 soon after Newton graduated from Cambridge
Went to his mother’s farm for two years and conducted optical experiments
Separated white light into colors with a prism
Could have concluded that the colors were created in the prism
Showed that wasn’t the case: used second, reversed prism to recombine the colors to form white light
Prism experiments made Newton famous
Returned to Cambridge in 1667 and remained for 30 years
Became Lucasian professor of mathematics in 1669

3. A particular color sometimes corresponds to a range of wavelengths
Blue: ~ 485 nm (460 nm)
Cyan: ~500 nm (blue-green)
Green: 510 ~ 550 nm (530 nm)
Yellow: 570 ~ 590 nm (580 nm)
Red: 620 ~ 670 nm (650 nm)
Most of the time, however, we see non-spectral colors. We can see a color even when the wavelength of the corresponding spectral color is absent. There is more to color than wavelength!

4. Intensity Distribution
Most of the colors we see are not spectral colors, but instead have a distribution of intensity in wavelength.
For example, a color green may contain all other colors but with the intensity peaked at the wavelength 530 nm.
Our eyes cannot distinguish the colors that are composite from spectral colors. (different distributions may correspond to the same perceived color!)

5. Sample Intensity Distribution
-- Plots the relative intensity at each wavelength.
Relative Intensity
400 nm
500 nm
600 nm
700 nm

6. Historical Problems with Identifying Colors
Theoretical Problems
Numerous color concepts
Different theorists organize properties of color into different functional systems
Leonardo da Vinci (15th Century)
Newton – discovered spectrum and devised color circle
J.C. Le Blon – observed primary nature of red, yellow, blue and described hues from mixing (1756)
Moses Harris – published first color circle in full color (1766)

7. Different Color Wheels

8. Various Color Classifications

9. Munsell Solves Color Problems!
Albert H. Munsell
Seascape painter of the 1890s
Munsell System of Color Notation (1905)
One of the color standards used by the US National Bureau of Standards
Used in science, industry, and art

10. What is the Munsell Color Tree?
3D Spherical Model
Incorporates concepts of hue, lightness, and saturation in one model
Organized in a numerical classification system
Inclusive of all colors – each color has its own place

11. Munsell Color Tree Based on the 2D Color Wheel
Includes primary, secondary colors, i.e. hues
Can be expanded to include intermediate hues
Shows all variations of colors/hues, which are at full intensity on the wheel

12. Munsell Color Tree Lightness scale - the “trunk”
The lightness/darkness of a particular hue
Vertical arrangement: the trunk of the color tree
Nine levels of lightness
1 = black
9 = white
Values of hues are compared with this neutral gray pole

13. Munsell Color Tree Saturation Fourteen levels of saturation
Refers to strength/weakness of a hue at a certain lightness
Related to purity, intensity
Horizontal arrangement: the branches of the tree
Fourteen levels of saturation
1 = dullest, most gray variation of the hue
14 = most intense, pure state of the hue

14. Lightness and Saturation

15. Classification of colors
Hue: main color. Associated with the “dominant wavelength” in an intensity distribution curve.
Saturation: purity of the color.
Measures how much dominant wavelength there is compared to the amount of white mixed in.
Saturated: all intensity fairly close to the dominant wavelength (spectral color is 100%)
White or grey: completely unsaturated

16. Brightness (light source) and lightness (surfaces)
Lightness has to do with the percentage of incident light reflected at each wavelength. (white: a lot of reflection; black: no reflection)

17. Color tree: The same position has the same color independent of the intensity!
Trunk completely unsaturated. Out from the trunk, the degree of saturation increases.
The vertical axis is related to lightness (a gray scale from white at the top to black at the bottom)
The hue varies around the tree (green,blue, red, etc.). Saturated colors are the “leaves” at the ends of the branches.
Color Tree

18. Color in Art

19. Mark Rothko (1956) Orange and Yellow

20. Henri Matisse ( )
Icarus (Jazz)

21. Josef Albers (1966)
White Line Square XIII

22. Piet Mondrian (1922)
Composition with Blue, Yellow, Black, and Red

23. Marc Chagall (1913)
Paris Through My Window

24. The End