Revelation 9:17 describes breastplates that are fiery red, dark blue, and sulfur yellow—colors John sees in his apocalyptic vision of fearsome cavalry. The hyacinth color suggests deep blue or violet, possibly with reddish tones, contributing to the overall ominous appearance of these supernatural warriors. Ancient interpreters sometimes associated this color with smoke or darkness. The specific color detail adds to the vivid, unsettling nature of John's vision, where every element contributes to an impression of supernatural terror and divine judgment.