Current study describes the occurrence of the PMEL17 mutation that causes the Silver phenotype on the example of an Estonian horse called Muuksi Tuul. The aim of the research is to explain the diluting effect in mane and tail of the PMEL17 mutation which is also associated with several eye disorders (MCOA syndrome) e.g. cysts and cataracts. In addition to the studies about individual horses, the research offers a possible reason to the wide range of Estonian horse coat colours and gives a possible answer to the origin of the Silver gene in its genotype. Furthermore, the research tries to fill the gap between new knowledge in colour genetics and linguistically used colour terms, proposing one possible solution for creating a system for the designations of the (Estonian) horse coat colours.