I'm a newcomer, but I'm going to take a stab at both the Black Irish
question as well as your name.
I believe Kathryn falls into the Caitlin group.
I was always told as a kid that the Black Irish were the result of
"ajoining" between Spaniards who went ashore from the famed Spanish
Armada of 1588 and native Irish. However, I did some research about the
Celts this summer. I'm taking this quote from John King's THE CELTIC
DRUIDS' YEAR. "In the first century BC, the historian Diodorus Siculus
wrote the following description of the Celtic peoples who were now
succombing to Roman rule: 'They are very tall in stature, with rippling
muscles under clear white skin. Their hair is blond, but not naturally
so: they bleach it, to this day, artificially, washing it in lime and
combing it back from their foreheads. They look like wood-demons, their
hair thick and shaggy like a horse's mane...." If Siculus wrote the
truth, then we know the early Celts' hair was darker than blond, dark
enough to show contrast from their lime-wash. The Romans were dark
haired, and we know they inter-mixed (inter-married?) with the natives.
I don't know about the Normans. The Vikings (Danes) were red-haired,
and the traditional protrait of an Irish lass with flaming hair may
indicate she has genes from the Viking pool. Between the early Celts,
the Romans, (anyone know about the coloring of the Normans?), and the
Spaniards, it seems likely to me that to be dark is more "Irish" than to
be red-haired if you want to go all the way back to about 200 BC when
the first Celts made their way to Ireland. Since the Vikings invaded in
the 11th Century (I think), red hair goes back a long way, but not
nearly as far back as dark.