What is a color space?
A color space is a method by which we can specify, create and visualize color. As humans, we may define a color by its attributes of brightness, hue and colorfulness. A computer may describe a color using the amounts of red, green and blue phosphor emission required to match a color. A printing press may produce a specific color in terms of the reluctance and absorbance of cyan, magenta, yellow and black inks on the printing paper.
A color is thus usually specified using three co-ordinates, or parameters. These parameters describe the position of the color within the color space being used. They do not tell us what the color is, that depends on what color space is being used.
An analogy to this is that I could tell you where I live by giving directions from the local garage, those directions only mean anything if you know the location of the garage before hand. If you don’t know where the garage is the instructions are meaningless.
Why is there more than one color space?
Different color spaces are better for different applications, for example some equipment has limiting factors that dictate the size and type of color space that can be used.
Some color spaces are perceptually linear, i.e. a 10 unit change in stimulus will produce the same change in perception wherever it is applied. Many color spaces, particularly in computer graphics, are not linear in this way.
Some color spaces are intuitive to use, i.e. it is easy for the user to navigate within them and creating desired colors is relatively easy. Other spaces are confusing for the user with parameters with abstract relationships to the perceived color.
Finally, some color spaces are tied to a specific piece of equipment (i.e. are device dependent) while others are equally valid on whatever device they are used.
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