If something is opalescent, it does with light what an opal does: the colour is not one colour. It shifts as you move, a soft shine, often a bit milky, with other colours sliding under the surface. Soap bubbles, some shells, certain glass, and the inside of a pearl can look like this. It is a rather fancy describing word — more at home in a story or a shop window than in the lunch line. A nearby word is iridescent, which also means colour that moves with light. Opalescent tends to feel creamier and cloudier; iridescent can be sharper, like oil on a puddle. You can use both of the same bubble and not be wrong; they just lean a little differently.

帶蛋白石光澤的；會隨光線變色的