Adobe illustrator 10 Manuale Utente

RGB colors are called additive colors because you create white by adding R, G, and B 
together—that is, all light is reflected back to the eye. Additive colors are used for lighting, 
television, and computer monitors. Your monitor, for example, creates color by emitting 
light through red, green, and blue phosphors.

Additive colors (RGB)

You can work with color values using the RGB color mode, which is based on the RGB color 
model. In RGB mode, each of the RGB components can use a value ranging from 0 (black) 
to 255 (white). For example, a bright red color might have an R value of 246, a G value of 
20, and a B value of 50. When the values of all three components are equal, the result is a 
shade of gray. When the value of all components is 255, the result is pure white; when all 
components have values of 0, the result is pure black.

Illustrator also includes a modified RGB color model called Web Safe RGB, which includes 
only those RGB colors that are appropriate for use on the Web.

Whereas the RGB model depends on a light source to create color, the CMYK model is 
based on the light-absorbing quality of ink printed on paper. As white light strikes trans-
lucent inks, a portion of the spectrum is absorbed. Color that is not absorbed is reflected 
back to your eye.

Combining pure cyan (C), magenta (M), and yellow (Y) pigments would result in black by 
absorbing, or subtracting, all colors. For this reason they are called subtractive colors. Black 
(K) ink is added for better shadow density. (The letter K came into use because black is the 
“key” color for registering other colors, and because the letter B also stands for blue.) 
Combining these inks to reproduce color is called four-color process printing.

Subtractive color (CMYK)