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Newton & Maxwell Color Spectrum ("Roy G. Biv")

Isaac Newton separated the colors of the rainbow from sunlight using a prism in 1672. Then in 1865, James Clerk Maxwell showed that radio waves, microwaves, X-rays, gamma rays, and visible light are actually all electromagnetic waves of varying frequency. Our eyes detect only a very small range of these frequencies.

Red Orange Yellow Green Blue Indigo Violet

Newton's Prism Setup, 1672

Sir Isaac

J.C. Maxwell

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RGB Color Mixing

  • RGB stands for the colors Red, Green, and Blue.
  • The human eye has “cone” cells activated by certain colors of light: L cones (red light), M cones (green), and S cones (blue).
  • Your brain combines signals from the 3 types of cone cells to “see” every color. On a TrueColor monitor like our iMacs', you can set the red, green, and blue light intensity of each pixel from 0 to 255, to get 16,277,216 colors. Displays that use 3 bytes for color are said to have “24-bit color depth” (about 16 million colors).

Red

255,0,0

#FF0000

​

Yellow

255,255,0

#FFFF00

Cyan

0,255,255

#00FFFF

Green

0,255,0

#00FF00

Blue

0,0,255

#0000FF

White

255,255,255

#FFFFFF

Magenta

255,0,255

#FF00FF

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Hue, Saturation, & Brightness (HSB)

In 1931 color TV engineers developed the HSB scheme for specifying colors. [HSB = Hue, Saturation, Brightness]. HSB fits human intuition better than RGB.

Mathematically HSB changes the RGB "color cube" into a cylinder. The ends of the visible spectrum join at what is called the "line of purples" (see dotted line above).

"Hue" is a single number that assigns each color a number from 0 thru 360 (degrees).

"Saturation" refers to the intensity of the color (0%-100%). A hue of saturation 0% will be gray or black; 100%, pure color.

Brightness (0%-100%) ranges from very dark (0%=black) to very bright (100%=white). Half the possible range is shown above.

0o

360o

120o

240o