Why is foam of different colour soaps , always white ?

We use different colour of soap to bath. No matter what is the colour of soap, the foam we get is always white. Why is it so ?

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No substance has its own colour. We see a substance of a particular colour depending on whether it absorbs or reflects the light spectrum falling on it. In other words, light spectrum is made of 7 colours : violet , indigo , blue , green , yellow , orange , red . When light falls on a substance, it will either reflect or absorb anyone or combination of colours. For ex, a green leaf reflects only the green wavelength of light spectrum and hence looks green . Similarly for blue colour of sky , red rose etc . Sometimes we see colours other than above said like pink . This may be due to combination of colours. Foam of soap is large bunch of bubbles which is made up of thin soap solution and some air . If the bubbles don't reflect any perticular colour ,then this state of colorlessness is called WHITE COLOUR . That's why foam is white. Now what if a substance absorb all the colours ? IT RESULT IN THE COLOUR BLACK . Remember black holes? They don't allow anything to pass through them because of their gravity hence look black .