Visual:
* Arcing: Emphasizing its curved shape.
* Vibrant: Highlighting its bright colors.
* Ethereal: Suggesting a mystical or otherworldly quality.
* Prismatic: Referring to the way it breaks light into its colors.
* Spectacular: Describing its impressive beauty.
* Multicolored: Stating its obvious color variety.
* Scintillating: Emphasizing its sparkle and shine.
* Serpentine: Comparing its shape to a snake.
* Jewel-toned: Emphasizing the richness and intensity of its colors.
Emotional:
* Mesmerizing: Evoking its captivating nature.
* Inspiring: Suggesting its awe-inspiring quality.
* Hopeful: Connecting it to positive emotions.
* Joyful: Representing happiness and cheerfulness.
* Tranquil: Expressing peace and serenity.
* Magical: Evoking its enchanting and mystical qualities.
Literary:
* Celestial arc: A more poetic way to describe its shape.
* Nature's masterpiece: Emphasizing its natural beauty.
* A promise of peace: Linking it to a common myth.
* A bridge to heaven: Emphasizing its ethereal nature.
* A symbol of hope: Highlighting its hopeful connotations.
Other:
* Ephemeral: Reflecting its fleeting nature.
* Rare: Describing its infrequent appearance.
* Striking: Emphasizing its impact on the viewer.
* Gorgeous: Expressing its undeniable beauty.
You can combine these words to create even richer descriptions, like "a vibrant, arcing rainbow", or "a mesmerizing, ethereal celestial arc".