Sure, some may look off-putting in the bullet, but on the lips, they transform into the most flattering hues. How? It's all thanks to a dye called Red 27. "[It's] a red dye which is colorless when dissolved in a waterless base," explains The Beauty Brains , a website run by cosmetic chemists Randy Schueller and Perry Romanowski. "When it comes in contact with moisture, the change in solubility and pH causes the dye to turn bright-pink," the site reads . "The product appears to change with your personal chemistry because the color changes when it comes in contact with moisture, [which] can come from your skin or even just the humidity in the air."