The Van pattern is named after Lake Van in eastern Turkey and not after the commercial vehicle in Great Britain. It is a very particular coat pattern.
The Cat Fanciers’ Association breed standard for the Turkish Van defines what the Van pattern is. The cat’s body should be chalk white (due to the presence of the piebald gene – also called the white spotting gene) with an inverted V pattern around the ears and forehead and a coloured tail. The colours for the inverted V pattern and the tail are red (orange) black, blue (dilute black), cream (dilute red?). The colours can be solid or tabby. The association allows some dark spots on the chalk white body but prefer an all-white, clean looking body.
It is the coat that adorns the Turkish Van cat according to the largest cat association in the world. The Van pattern is what distinguishes the Turkish Van from other cat breeds.
However, it is an artificial breed standard. It is a Western creation probably born out of the fact (is it fact?) that the first Van cats to make it to the West had these coat patterns.
However, in Turkey, the Turkish Van is said to the same cat as the Turkish Angora and you will see these cats in a wide range of colours and coat types. You will see the Van pattern but it is not the only coat type. Perhaps the Turkish people prefer predominantly white cats but that is not the only colour.
Whenever, I see pictures of street cats, also called community cats or feral cats, in the area I have selected in the map(s) below (I have added a second map), I often see the Van pattern. The location of the origin of the Van pattern does seem to be centered around eastern Turkey but it spreads out substantially over many of the countries surrounding the Mediterranean Sea especially to the east and south.
That is my impression. It is not based on science and neither does the information come out of a book or website. It is simply what seems to be the case to me. I am happy to be corrected. Note: the pattern is not limited to this area. It just seems to be more common in this area.
I don’t think you will find any text or maps about where you are most likely to see Van patterned cats, namely: to eastern and southern Mediterranean – i.e. North Africa. This poor map, below, that I have made indicates where I believe you are most likely to see the Van pattern.
Updated, different or better map: