Umbratio

A natural hair color/state that is defined by constant distinct shifts in shades. A person with umbratio hair can have brown hair one day and then more blonde hair another.

It's found in people with various hair colors within their bloodline, and they're often not able to pin what color their hair actually is.

The colors shift with the amounts of humidity in the air, becoming different colors while still being dry. (As opposed to having darker hair when its damp/wet.)

From the Latin words "Umbra mutatio", meaning "Shade change". Pronounced, "Um-brA-se-o".