Why the foam of Coloured soap is white?

Soaps on the market are colorful

The same goes for shampoo

But the only thing in common is that

No matter what color soap or shampoo, etc.

The foam that comes out of the wash is white

So why?

The spherical surface of soap solution film

Strong refraction of light

After the reflected light is scattered everywhere

In the human eye, it appears white

And the foam itself is colorless

The light either penetrates

or is specularly reflected

When many bubbles are crowded together

Specular reflection of each foam

will be concentrated together to become a diffuse reflection

For example, polar bear hair is transparent

But together it is white