Literature Reference: 送秦光禄北征 —— 作者：李贺
北虏胶堪折，秋沙乱晓鼙。
髯胡频犯塞，骄气似横霓。 Sending General Qin on the Northern Expedition —— By Li He
The northern invaders' bonds can be broken, the autumn sands disturb the dawn drums.
The bearded barbarians frequently breach the borders, their arrogance like a horizontal rainbow.
横: Horizontal or vertical, it's all the same. Opposed to "longitudinal."
霓:
The radiant arc of the rainbow, embodying a holistic understanding and a striking beauty.
Meaning: The horizontal rainbow symbolizes splendor and hope across the sky.