Mithra and the bull, fresco of Dura Europos, datable after 168 and before 256 CE

Source: Wikipedia
The fresco shows the mouth of a cave where Mithra, in a light colored toga
, straddles the bull, his knee on its back, pulling its head up by the ears.  Mithra is dressed in a light colored toga, his hair braided, a helmet on his head and a shield over his shoulder.  Mithra is looking away from the bull and toward the left.

The bull is white.  His muzzle is red, and blood streams from a wound in his side.  In front of the bull, but in the background, stands another soldier, sword in hand, blade pointed toward the ground.