A: Well, what you are seeing isn’t actually a color change. Gray hair looks “white” because it is lacking in pigment (or has a
significantly reduced amount of pigment). Hair naturally is somewhat translucent, allowing light to shine through and create a
“glow in the hair” when in bright light. It’s the density of the amount of pigment in the hair that creates the subtle variation in the hair’s natural color.
When hair turns gray and loses its natural pigmentation, the hair is even more translucent, and
reflects and refracts more light. When gray hair is wet, it is weighted down and plastered against the other hairs on the head by
moisture, which makes the hair more transparent. The wet hair magnifies the color of any other hairs nearby and isn’t easily
penetrated by light, so the hair itself looks darker.
The exact shade of the “apparent” color of the gray hair when wet depends on the pigment in the
hair that is not gray. I know many men who are salt and pepper gray, whose hair appears inky black when wet.
For what it’s worth, this is the exact same principle that causes any hair color to appear
darker when the hair is wet. When the hair is dry, more space exists between the hairs, thus more light penetrates and the color
appears brighter and more luminous.