there is such a kind of lipstick, its paste may look basically colorless, or even be made into a strange color such as green, but when applied to the lips, its color will slowly turn pink. How does this effect work?

Let's first take a look at a list of ingredients of discolored lipstick:

the front lists a lot of waxes, oils and various extracts, which are not specific to the ingredients of ordinary colorless lipstick. The real trick lies in the last item on the composition list: CI45410:1. This is the color number of the pigment component, which represents a red pigment component. There are many names for this ingredient. It can be "Draco C Red 27" or "solvent Red 48". In short, it refers to the molecule in the picture below:

this ingredient is actually used in many kinds of discoloration lipstick. This molecule is actually colorless in a non-dissociated state, as is the case when it is present in lipstick, when it is surrounded by a non-aqueous matrix such as wax and oil. When it comes into contact with water and the pH is not too low, it begins to change to an ionic state, which shows red because of changes in electron distribution (discoloration occurs in the case of pH3.4~5.0, which can be understood as an acid-base indicator). And this is the principle of lipstick discoloration, when applied, the pigment molecules in the thin layer come into contact with the surrounding water, will slowly change to colored form.

some discoloration lipstick mentions that everyone changes to a different color, or "changes according to mood", but it's not that magical. The moisture in the environment may be different, and the pH on the surface of each person's skin is not exactly the same, but basically the discoloration effect will not be much different. If the color looks different, it may have something to do with the background color of the lips.

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not all pigments can change color, so the color of discolored lipstick is actually limited, which has no advantage over ordinary colored lipstick, but it's interesting to watch transparent lipstick gradually change color. Think of it as playing with _ (: painting "∠) _

reference: https://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/reddyes_508.pdf

https://intothegloss.com/2015/02/color-changing-lipsticks/