Why is, no matter the colour of the shampoo, the foam always white?

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Why is, no matter the colour of the shampoo, the foam always white?

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Anonymous 0 Comments

The color of the foam is not caused by the color of the liquid, but the color of the light diffraction on the edge of tiny individual bubbles.

Imagine two bubbles of soap that are touching each other. The main surface of each bubble will probably be sort of rainbow shimmery, right? But what color is the line where the two bubbles meet, when viewed edge on? Basically, all the colors of the rainbow stacked on top of each other, which is to say, white light. Soap foam is millions of tiny bubbles all touching each other, which means that instead of the big round swell of a floating soap bubble, it is almost all just the edges where two or more bubbles are touching each other.