Fudo Blue Black
This colour was based on the colour of the body of Fudo Myo-o. In the Jyu-Kyu Kan text, the skin coloration of Fudo Myo-o is described as blue-black. While there are other colorations of Fudo Myo-o, this particular colour is inspired by that text and I feel is a good, strong colour for Fudo Myo-o.