phy1020.DVI

see the red and green pixels turned on, and the blue pixels turned off. To form orange, the red pixels will be
on and bright, the green pixels on but dim, and the blue pixels will be off.

56.2 Pigments

Coloredpigmentslike paints and inks work differently from lights. If a colored pigment is illuminated
with white light, it will absorb some colors and reflect others; the combination of the reflected light colors
determines the color of the pigment.
Students of art are often taught that the primary colors for paints are red, yellow, and blue, but this
isn’t quite right. For pigments like paints, the primary colors are the same as thesecondarycolors of light:
magenta, yellow, and cyan. Magenta paint absorbs its complementary color (green) and reflects red and blue
light; yellow paint absorbs its complement (blue) and reflects red and green light; and cyan paint absorbs its
complement (red) and reflects green and blue light (Table 56-3).

Table 56-3. Pigment colors.

Made by

Pigment combining Absorbs Reflects

red magenta & yellow green & blue red

green cyan & yellow red & blue green

blue cyan & magneta red & green blue

cyan cyan red green & blue

magenta magenta green red & blue

yellow yellow blue red & green

white none none all

black all all none

Likewise, thesecondarycolors for pigments are the same as theprimarycolors for lights: red, green, and
blue. In each case, a pigment of one of the secondary colors reflects only that color, and absorbs the others.
The color that results by mixing pigments can generally be predicted^1 by assuming that the mixture will
absorb the colors of its components, and reflect everything else. For example, what happens if we mix cyan
and yellow paint? The cyan pigment absorbs red, the yellow pigment absorbs blue, and so the mixture should
absorb both red and blue, and reflect green; thus cyan and yellow pigments mixed together make green.
Table 56-3 shows the colors resulting by combining colors inequal amounts. Other colors can be created
by combining pigments in ways that reflect the primary light colors in unequal amounts. For example,
suppose we combine red and yellow pigments. The red component of the mixture will absorb green and blue
light, while the yellow component will absorb blue light. The mixture will then absorb some green light, and
lots of blue light — resulting in the reflection of lots of red light and some green light, and anorangecolor.

56.3 Spectral Colors

If white light is split into its component colors (aspectrum) using a prism or diffraction grating, we observe
the colors listed in Table 56-1, called thespectral colors. The spectrum includes the primary colors of light
(red, green, and blue), along with the secondary colors yellow and cyan (located between green and blue).

(^1) Assuming the pigments do not react chemically.