The breed standard recognizes four colors: Blenheim (chestnut and white), tricolor (black/white/tan), black and tan, and ruby. While heart disease is common in dogs generally – one in 10 of all dogs will eventually have heart problems – mitral valve disease is generally (as in humans) a disease of old age. The 'hinge' on the heart's mitral valve loosens and can gradually deteriorate, along with the valve's flaps, causing a heart murmur (as blood seeps through the valve between heartbeats) then congestive heart failure.