system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is all soap foam white, regardless of the color of the soap?
gpt
Color can be made a few different ways. When sunlight goes through colored glass, some of the light doesn’t get through and the color we see is the stuff that did get through. 

A colored bar of soap is that color because when light hits it, some bounces off but not all of it, and we see the combined colors that did bounce off. 

Soap bubbles work slightly different to both of these. Rather than absorbing any of the colors, they just sort of bounce the light off equally in all directions and that just looks like white. The surface of the bubble is mostly made of things in the soap that aren’t colored, and some water. So you’ve got barely any of the colored stuff in the bubble, and the way the bubble itself behaves with the light makes it look white.