The lighter highlighed colour combinations are not allowed in Italy
Merle x merle breeding produces the so-called double-merles or white-merles, they may be defective in hearing and/or vision.
Sable-merles or darksable-merles can sometimes be very difficult to identify, usually the merling can be seen on puppies only. A knowledge of the parents genytypes is required. To avoid a sable-merle x sable-merle mating, thie breeding of sable-merles is not allowed as well.
White Collies are 90-99 percent all white and are homozygous for the white factor sw. The head of the White Collie is coloured according to its genotype (sable, tricolour, blue-merle). As the collie is a British breed, England is responsible for Collie standard. In the actual standard, the colour white is not a recognised Collie colour and may lead to a disqualification on shows and selections. In the USA the White Collie is permitted to be exhibited, the colour white is an additional colour in the US standard.
The White Collie is a healthy dog as sable and tricolours, and is on its way to win more and more popularity in Europe. The White Collie has noting to do with a double-merle which may be defective