No magic here -How do cosmetics change colour on skin.

Can cosmetics like Smashbox's O-glow somehow detect your natural skin tone or even your emotional state and then adjust their colour to match? uh... NO. So how does it work?

1. Ingredients that change color with pH/solubility

A colourant known as “Red 27,” a red dye which is colourless when dissolved in a waterless base. When it comes in contact with moisture, the change in solubility and pH causes the dye to turn bright pink. The product appears to change with your personal chemistry because the colour changes when it comes in contact with moisture can come from your skin, or even just the humidity in the air.

2. Encapsulated colors
Some products use colourants that are coated with waxy or gel-like ingredients and suspended in an uncoloured base. When the product is rubbed into your skin the friction breaks open the dye capsules releasing the colour. The product appears to change with your personal chemistry because the more your rub in the colour, the more is released

3. Skin protein reaction
Products that provide a “natural tan glow” work by using an ingredient called “dihydroxyacetone” or DHA. This chemical reacts with the keratin protein in the upper layers of your skin, staining them a light orangish-brown colour. The product appears to change with your personal chemistry because it uses low levels of DHA that provides a very gradual change in skin colour. The more you use, the more pronounced the “glow” effect is.