Points (fur color)
In cats, a point is a dark coloration of tail, face, ears, and paws. It is often, but not always, quite dark and may be black.Points are found in several cat breeds and are part of the standard in most of them, but not all. Especially in lighter colored cats (eg, the Siamese) the points can be of several shades. If not black, or at least quite dark, they are often referred to as colourpoints.
The cause is a gene which is heat sensitive. When cooler (ie, on tail, ears, etc) pigment is expressed, and hairs are darkly tinted. When on warmer skin surfaces, the gene's operation is repressed. In most breeds, points are not apparent at birth, there having been little temperature difference in the womb. They begin to appear after several weeks.
The effect can be quite striking, as in Siamese and other similar breeds or more subtle, as in the 'natural mink' Tonkinese.