Chemistry behind lip balm coloring based on skin pH
CI 45410 (A.K.A. Phloxine B or acid red 92) is a pH dependent dye which is clear below about pH=4.1 and pink at pH>4. The formulation is mildly acidic and is neutralised by saliva upon application to become pink.  

(Thereby "uniquely creating the perfect shade of pink lips just for you.")