Black is usually associated with the "dark side" -- evil, frightening, and negative. But in the Way of Tea, a black chawan (tea bowl) is prized above all others.
This is partly due to the fact that the great tea master Sen no Rikyu favored black chawan, a preference some say may have cost him his life. Even though he knew that his lord, Hideyoshi, despised black (it supposedly reminded him of his lower-class upbringing), Rikyu dared to serve him tea in a black chawan. It was the perfect vessel for his wabi cha: a Zen-like universe in a black hole.
Rikyu particularly loved a Setoguro (black Seto) chawan known as Oharagi (Ohara wood), and the inscription on the lid of its box is attributed to him; it is a treasure of the tea world.