In "A Rose for Emily," what is meaningful in the final detail that the strand of hair on the second pillow is iron-gray?

The
surprising fact thrown in almost casually at the end of the story is what gives the whole tale
its Southern Gothic impact. Not only did Missretain the corpse of her dead beau in her home for
decades; not only did she poisonin order to keep him; not only had the decaying body caused a
stench that the whole town noticed--these events would have been creepy enough. But Faulkner
adds another gruesome detail that tops them all: Miss Emily has been sleeping with the corpse
years after Homer Barron's murder.

Faulkner makes it clear that when Miss
Emily and Homer Barron were courting, Miss Emily's hair had not yet turned gray. Miss Emily's
hair began turning gray "some time" after the mysterious disappearance of Homer Barron
and a period when Miss Emily did not leave the house. Even then, it was not the
"salt-and-pepper iron-gray" that it eventually became and...