What is Colour? (Explaining Melanin)

What a ridiculous question! And yet, it is the basis for every expressed colouration sequence. (Obviously.)
One thing to keep in mind is that every dog coat colour is genetically black. Regardless of how the colour is actually expressed, the coat's genetic makeup itself is based on the production of melanin. Melanin is then altered in various shades and for various reasons, thus producing the wide variety seen in coat colours.

This Melanin is then divided into two subgroups, which are the foundation for all colours expressed. Any alterations are then explained by the genotype sequencing.
As there are so many colours and colour combinations, I have only included the very base solids (black) and (red). Keep in mind these solids alone come in a great variety of colours - blues, browns, creams, off-whites, etc, as well as numerous patterning.

Melanin Divided - Eumelanin.
Eumelanin is the expression of the black Melanin. A variety of forms occurs (which will later be discussed). Eumelanin controls black pigment and all expressions thereof. Also affects colour intensity of the eyes, nose, skin, and eye rims.
 

Melanin Divided -  Phaomelanin.
Phaomelanin - this is the red factoring pigment. Present only when Eumelanin is not, or, in some instances (such as a black and tan dog), is expressed alongside black areas. The Phaomelanin is then controlled by colour intensity factors which determine whether a dog will be dark red, tan, or whitish cream. Phaomelanin differs to melanin in that it does not affect eye colour, nor skin colour, nor does it have an overall effect on genetically black dogs. Phaomelanin is recessive to Eumelanin.

Next, I will attempt to explain some of the basic colours (namely, the base colour 'black' and its forms) as mentioned above, and will also add some of the more confusing colour patterns. These will, of course, be included later, after our general foundation of the black dog and its gene sequencing.
I will also mention white and white patterns further along.