An RGB value by itself has no meaning. It's the color model that defines how the three components interact within a color space to define a color. Graphically, a point in a three-dimensional grid or cube represents a color. Each dimension (or axis) corresponds to a different channel. The RGB color model is then a cubic , or Cartesian , coordinate system of the underlying color space.

For the web, the underlying color space for an RGB value is sRGB (Standard RGB), and each RGB component is a number between 0 and 1.

Note that sRGB is one of several RGB color spaces . Other RGB color spaces, like the Adobe RGB color space, can represent a wider gamut of color than the sRGB color space. The coordinates in sRGB and Adobe RGB are different.

There are many ways to describe the RGB components of a color. In CSS , they can be represented in various ways: in hexadecimal notation as a single 24-bit integer (for example, #add8e6 is light blue) or in functional notation by using rgb() with three percent values or numbers ranging from 0 to 255 (for example, rgb(46 139 87) is green). CSS also supports the srgb , srgb-linear , a98-rgb , and prophoto-rgb color spaces for the color() function.

RGB is not the only color model that can represent the sRGB color space . Cylindrical coordinate systems like the HSL (hue-saturation-lightness ) or HWB (hue-whiteness-blackness ) color models are also used to represent an sRGB color on the web.