 The four sets of markings reflect the four former breeds from which the modern breed was derived . Black and tan markings are known as " King Charles " , while " Prince Charles " is tricoloured , " Blenheim " is red and white , and " Ruby " is a single @-@ coloured solid rich red . The " King Charles " black and tan markings typically consist of a black coat with mahogany / tan markings on the face , legs and chest and under the tail . The tricoloured " Prince Charles " is mostly white with black patches and mahogany / tan markings in similar locations to the " King Charles " . The " Blenheim " has a white coat with red patches , and should have a distinctive red spot in the center of the skull . 
