RGB in a book!
The RGB Colorspace Atlas
Human eyes typically have three types of color receptor on their retinas, each sensitive to a different range of wavelengths of light. The colors associated with these wavelengths are approximately red, green, and blue. Because there are three types of color receptor, it is possible to map the visible spectrum in a three-dimensional spatial model by assigning red, green, and blue each to a dimension.
It is then possible to outline a cube in this space, where the values of red (R), green (G), and blue (B) are visible on a gradient scale of 0 to 100% in their respective directions. These gradients combine to create the RGB color space cube, a volume in which any color can be located by a set of three coordinates.