First, the lipstick work not by reacting with the pH of your lips but actually with the moisture of your lips. This reaction is caused by Red dye 27, which is an FDA approved dye safe for drugs and cosmetics that is colorless unless exposed to moisture. So once you put the lipstick on your lips, the color will change to a red or pink hue depending on how the lipstick is made. Don't worry, just because the lipstick reacts with the moisture on your lips doesn't mean that it sucks the moisture out of them! Also, don't expect the lipstick to look the same on everyone. The final tint of the color that ends up on your lips is dependent on what color your lips started with.