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As we know foam is white regardless of the color of the soap or shampoo.

... the foam in its entirety looks white because when light enters the soap solution, it must pass through a number of tiny soap bubbles, i.e., a number of surfaces. These countless surfaces scatter the light in different directions, which makes the foam/lather look white.

My question is that is it possible to have colorful foams? For example, can we use water insoluble pigments in the process of making soaps and shampoos in order to have colorful foams?

Snack Exchange
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  • You mustn't have encountered crazy/funny foam in your life (it apparently has made a comeback but was a 90's thing). It is exactly colored foam as you ask...but I can't find a good link for it. – Triatticus Jul 19 '23 at 12:50
  • Oh, yes! I recall what you're talking about. I think you're talking about the experiment that a chemical solution is added to a toothpaste or dishwashing liquid and the result is expansion of the cleansing material with a foam with the same color with the chemical compound. I think there was an elephant in the name of the experiment. – Snack Exchange Jul 19 '23 at 13:55
  • Here is a good link: https://www.scienceabc.com/eyeopeners/why-is-soap-foamlather-always-white-colored.html but history has shown that empirical observation can sometimes trounce theory. So, try this experiment and gather your conclusion. – Nilay Ghosh Aug 17 '23 at 17:20

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