All hair color is the result of a combination of three pigments found within the cortex of the hair.
These three pigments are:
  • eumelanin- these extremely tiny, round pigment molecules are characteristically strong with blue pigment, yet are physically very weak.

  • erythromelanin- very large, round molecules that are attributed with red pigment.

  • phaeomelanin- irregularly shaped, sticky molecules responsible for yellow pigment in the hair. because of their shape and stickiness, they are extremely strong and difficult to remove from the hair.

Since eumelanin is physically weak, it is easy to remove from the hair. Which constitutes the reason that so many people find unwanted warmth in their hair.