In the diploma thesis we present the colour types of horses and the most typical white spots on the body, head and legs. We've focused on genes for determining the colour of horse hair. The genes were divided into several groups, those responsible for basic colours, colour dilution, graying and the genes which determin depigmentation and patterns. Within each gene, we have accurately described the way a particular colour was inherited and reflected on the offspring or specimens that have this gene. We've also listed some of the breed representatives that are characterized by the presence of a particular gene. More specifically, we've focused on description and functioning of characteristic genes in the Appaloosa and Lippizaner breeds. We've discovered that the colour pattern of the Appaloosa horse was very different, depending on at least two genes that cause different colour patterns within a single gene. The characteristic feature of Lippizaners shows that some specimens, beside the presence of a gene for graying and the typical colour, preserve black or brown, original colour during their whole lives. The most important topic for breeders was described at the end. It refers to tests that determine the colour of the horse. We have described some important tests for determining descendants of certain colour types of horses.