 Rocky Mountain Horses stand between 14 @.@ 2 and 16 hands ( 58 and 64 inches , 147 and 163 cm ) high . Any solid color is accepted by the registry , but a dark brown color called " chocolate " with a pale , " flaxen " mane and tail is preferred . This coloration is the result of the relatively rare silver dapple gene acting on a black base coat . Although uncommon , this gene has been found in over a dozen breeds , including the Rocky Mountain Horse . Minimal white markings are accepted by the registry , although leg markings may not extend above the knee . The physical characteristics are somewhat variable , due to the disparate breeds that created the Rocky Mountain Horse . The Rocky Mountain Horse is known by enthusiasts for its hardiness and ability to withstand winters in the mountains . It is also praised for its good nature and affinity for humans . Rocky Mountain Horses have the highest risk of any breed for the genetic ocular syndrome multiple congenital ocular anomalies ( MCOA ) , originally called equine anterior segment dysgenesis ( ASD ) . MCOA is characterized by the abnormal development of some ocular tissues , which causes compromised vision , although generally of a mild form ; the disease is non @-@ progressive . Genetic studies have shown that the disorder may be tied to the silver dapple gene , as most horses diagnosed with MCOA carry the gene . 
 Rocky Mountain Horses stand between 14 @.@ 2 and 16 hands ( 58 and 64 inches , 147 and 163 cm ) high . Any solid color is accepted by the registry , but a dark brown color called " chocolate " with a pale , " flaxen " mane and tail <a href='drop_aux' title='1'><mark>is</mark></a>preferred . This coloration <a href='drop_aux' title='2'><mark>is</mark></a>the result of the relatively rare silver dapple gene acting on a black base coat . Although uncommon , this gene <a href='been_done' title='3'><mark>has</mark></a> been found in over a dozen breeds , including the Rocky Mountain Horse . Minimal white markings are accepted by the registry , although leg markings may not extend above <a href='None' title='4'><mark>the</mark></a><a href='negative_concord' title='5'><mark>knee</mark></a> . The physical characteristics <a href='drop_aux' title='6'><mark>are</mark></a>somewhat variable , due to the disparate breeds <a href='null_relcl' title='7'><mark>that</mark></a>created the Rocky Mountain Horse . The Rocky Mountain Horse is known by enthusiasts for its hardiness and ability to withstand winters in the mountains . It is also praised for its good nature and affinity for humans . Rocky Mountain Horses <a href='got' title='8'><mark>have</mark></a> the highest risk of any breed for the genetic ocular syndrome multiple congenital ocular anomalies ( MCOA ) , originally called equine anterior segment dysgenesis ( ASD ) . MCOA is characterized by the abnormal development of some ocular tissues , which <a href='uninflect' title='9'><mark>causes</mark></a> compromised vision , although generally of a mild form ; the disease is non @-@ progressive . Genetic studies <a href='been_done' title='10'><mark>have</mark></a> shown that the disorder may be tied to the silver dapple gene , as most horses diagnosed with MCOA carry the gene . 
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