Colloquially, does the term "redhead" apply specifically to a person with naturally red hair? [closed]

I'm no great respecter of dictionaries, but you're right: the dictionary does not discriminate. Anybody having red hair, no matter how the hue was acquired, is a redhead, by definition. Presumably this is true, at least transfiguratively, of somebody whose hair is colored by blood after a serious wound, and of somebody whose hair is so colored by a mere trick of the light.

Yet the notion that 'redhead' often connotes (as opposed to denotes) a genetically marked set of people is accurate. As one of those people, I can swear to it. In terms of evidence, I'll offer these, briefly:

1784 T. Holcroft Noble Peasant i. i. 7 Zounds, Clym, hast no religion?—Dost not know that these Red-heads, these Carroty-poles, are Pagans?
...
1893 K. Kohler in J. H. Barrows World's Parl. Relig. I. 366 You see man divided into groups of blackheads (the race of Ham) and redheads (Adam).
...
1998 Stornoway Gaz. 31 Dec. 8/5 Once a redhead always a redhead—you do not forgo membership if your red hair turns silver or even if you go bald.

[From "redhead, n. and adj.". OED Online. September 2015. Oxford University Press. http://www.oed.com/view/Entry/160309?redirectedFrom=redhead (accessed October 05, 2015).]

I refer you especially to the 1998 quote, and remark that while I was once compared to a "frayed copper wire", that is no longer a viable comparison (at least with reference to my outward appearance), yet I am still in my own thinking and in the thinking of those who have known me since then, a redhead.

The distinction which applies, I think, is between redhead and natural redhead.

Red hair has not been as widely valued, for instance, as blonde, which means there isn't as much experience with wannabe gingers. Bad blonde dye jobs have terms such as "bottle blonde" and "bleached blonde", but I don't think there is much precedent for a simple, one-word distinction between being born redheaded and acquiring it via artifice.

Being redheaded (as in carrot-top, which I was until I hit puberty) is usually accompanied by freckles, but I've seen children with red hair who were simply pale. Since I've seen similarly pale blondes, I don't think that it is possible in principle to tell the difference between a born redhead and the alternatives simply by appearance. This is especially true since there is no (to my knowledge) official standard for redheadedness. Dark hair with distinct red highlights is often called red.

I'm a Redhead, and so is my wife and kids...

Redhead is different than "blonde" or "brunette" because, as you hinted, it also carries the assumption that the person will have a fair complexion, and probably some degree of freckles. If you say someone is blonde, that is only a hair color - you can't really assume anything else about them.

I believe that the term redhead is closer to an ethnicity than just hair color in that sense. You can argue that redhead is only a hair color and "true redhead" implies the other features, but "colloquially", redhead is about more than just hair.

Of course I may be biased...

The term "red head" is not as common as what I usually hear, which is ginger. The slang is most likely different depending on the culture. One does usually associate a fair skin and perhaps freckles with a person with red hair but as Miss Clairol advertises, "Only her hairdresser knows for sure." Well, that and anyone who knows her intimately.

Usually "red head" or "ginger" is not enough distinction as people will also include "natural" or "true" so in that case, "red head" would be associated with the color of the hair if no more distinction is given. It would be no different than if the person was a brunette.

Blonde also requires distinction. A blonde is a person with blonde hair but there are also shades, like strawberry blonde, dirty blonde, etc. And to add more slang there is the California blonde, which implies the person is not a natural blonde, but a brunette who needs a touch up, usually a major touch up because there is usually as much brown as their is blonde showing. People can even request a California blonde look.

Again, this goes to culture. Since "red head" is slang, it doesn't appear there is an original distinction other than the color of the person's hair, natural or not.