Sorry, I didn't mean that as an attack. I just meant to say that to mean having/using/preferring orange_hair as a tag doesn't have any bearing on posts that auburn_hair would apply to.
And yes, your definition of auburn agrees with my understanding of the word: "a dark, saturated, reddish brown".
EDIT: Unless maybe you are saying that auburn = dark orange. Which I suppose could be an interpretation since browns share the same hues as reds and oranges. I'd argue that below a certain brightness and saturation though, the color ceases to be commonly called "orange" and either becomes "brown" or "burnt umber" or something else depending on factors other than hue. With respect to hair, a dark red or red-orange is often "auburn".
Go ahead with auburn, if you think you have good examples. I'm up for fairly granular hair colors, but with the understanding that most people won't think with that much granularity. And of course when it's ambiguous, multiple tags can be used.