Yamadharma Raja, or Yama, is the Hindu God of death. He is also referred as Kaala and both Yam and Kaala have the meaning controller of time. The vehicle or Vahana of Yama is a black He buffalo. Symbolically, the animal suggests the arrival of death senselessly.
There is a belief in some cultures that He Buffalo is one of the most senseless animals. Just like the buffalo, death arrives to us senselessly – and takes our life without looking age, status, religion or any other social parameters.
The black color represents the journey after death with Yama to the unknown destination.