I have blonde hair! I recently learned that it's characterized by low levels of the dark pigment eumelanin!
What the heck is eumelanin?  I have never heard that term before!
It's a pigment! Specific blond hues depend on many things, but I guess it always results in some sort of yellowish color. 
Interesting!  Are blondes more common that brunettes or is about equal?
Brown hair is a bit more common, but there is a huge rivalry between blondes and brunettes! It's really a cultural phenomenon in many countries including the US, Canada and the UK! I think that's kind of silly!
That is funny!  Why on earth would there be a rivalry over different color hair?
I don't know! You can't help what color hair you have! Not to mention, some blondes can also be considered brunettes! Blonde hair can range anywhere from very pale blonde to golden-brown! 
Isn't it true that some people hair color can change from blonde to brown as the get older?