SOAP IS IN DIFFERENT COLORS; BUT HOW THE FOAM IS WHITE?
Reflecting yellow color and when other colors are sucked, that object looks in yellow color. On that base, when all color is reflected, that object looks in white color. On the soft foil of soap which is filled up with air, air bubble is looming. The soft foil of the soap acts as a mirror and reflects all colors. Therefore all the air bubbles of the soap look in white color.