Similar idioms have purple gas coming from the east.

The initial word purple gas comes from the east [1] Pronunciation z z zǐ qì dōng lái i Interpretation Legend has it that before I passed the Hangu Pass, Yin Xi of Guanling saw the purple gas coming from the east, knowing that a saint must pass. Sure enough, I came riding a green cow. This old metaphor is a symbol of good luck. Used as object and attribute; Subject-predicate structure of positive purple gas coming from the east

There are several similar ones: Oriental purple, multicolored purple, Qing purple, Pei purple and HarmonyOS purple.