The classical colours of the siamese and the balinese are seal-, chocolate-, blue- and lilac-point.
The original and most common colour of the Siamese is black which is expressed as seal-point.
Mutations of the gene for black give rise to chocolate.
This color is thought to be
due to a smaller number of eumelanin granules in the hair shaft.
The chocolate color is a medium to dark brown color; it is sometimes called chestnut.
This gene os on the B (=brown) locus; chocolate is recessive to Black.
A mutation of the gene for dense coloration produces blue and lilac.
These colours are due to clustering of the particles of pigment in the hair shaft.
This is called dilution or maltesing.
Blue is the dilute form of black; it is commonly seen as various shades of gray.
Lilac is the dilute form of chocolate;
it is described as dove or light taupe gray,
and is sometimes called frost or lavender. Dilution is a mutation at the D (=dilution) locus;
dilution is recessive to dense coloration, that means it must be present twice (dd) that the
coat colour gets diluted.
Recommended links to other genetic sites can be found on the link page.