Computer Graphics/Color Models
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components. When this model is associated with a precise description of how the components are to be interpreted (viewing conditions, etc.), the resulting set of colors is called color space.
The XYZ Model
This standard was set in 1931 by the International Commission on Illumination(CIE).
It is not practically possible to create a perfect spectrum of all possible colors. Having said that, it is possible to get nearly all possible colors using a set of "primary colors". These primary colors are hypothetical. No real primary colors are defined.