Love Interests have always been Colour-Coded for Your Convenience. Traditionally, the hero’s significant other would usually be a blonde, to contrast with the brunette Vamp or Femme Fatale. But today, the passive Distressed Damsel and Shallow Love Interest have been replaced by the sassy, bold, brash, sharp-tongued Action Girl and Well, Excuse Me, Princess! — easily compatible with the “spunky Fiery Redhead” stereotype.

A good part of the time the hero’s redhead is actually calm, at least most of the time. When she is fiery she will probably be making him work to win her over for a long time or he won’t realize that she’s the one for him until the end.

Considering that less than 1% of the world’s population have red hair (largely confined to the Anglo-Irish sphere, and even there only tops at Scotland’s 13% of the population, and oddly enough also found in many Jews), there is a disproportionate number of red-haired female characters out there, and an inordinate number of them are The Hero’s winning Love Interest. (On top of that, she is also inordinately likely to have green eyes to go with it.)

Naturally, it’s quite common for the Veronica in a Betty and Veronica Love Triangle to be a redhead; the Betty will be a blonde.

One possible source is Robert A. Heinlein‘s fondness for hypercapable redhaired heroines (he had a red-haired wife).

In European comics, the high proportion of redheads among the main protagonists has been explained by some authors by the simple fact that, since redheads are rare, they’re easier to spot in the panels — especially true for crowd scenes.

Look out for the large number of Dark Skinned Redheads in Anime.

Perhaps surprisingly, given the (relatively) high proportion of Irish redheads, this trope does not seem to exist in Ireland. Redheaded female leads do appear of course, but they are heavily outnumbered by blondes and brunettes. This may be that unlike almost everywhere else red hair is not really seen as especially ‘exotic’ in Ireland.

There isn’t always a reason for this, if there is, sometimes the red hair is symbolic of love and romantic desire, or the author just finds girls that look like that appealing.

There are some cases where the redhead actually is the hero. This is the result of an Evolving Trope. (Maybe. Red-headed male heroes are as old as Gilgamesh.)