Source: Quests from the Infinite Staircase

Potion, Uncommon

When you drink this potion, you and everything you are wearing or carrying take on a rainbow-hued appearance for 1 hour. During that time, you can use a bonus action to turn any color or combination of colors you choose. If you mimic the colors of your surroundings, your hues continually shift to match your surroundings, and you have advantage on Dexterity (Stealth) checks until you change your colors again or the potion wears off.

The potion is separated into seven brightly colored bands of immiscible liquids and has a syrupy taste.