[Cronos]

Scots-Irish-Welsh are not always blue-eyed and freckled--look at Catherine Zeta Jones

Actually the Welsh are supposed to be dark haired and brown skinned -- the English call them dark welsh (not meaning tha tthey were negroid, just darker than the blue-eyed blonde English) -- the blue eyed blonde Scots are mostly due to intermingling of the blood with Norsemen

[ZULU]

The Welsh are decended from the original British inhabitants of England prior to the Anglo-Saxon Invasions.
They are a Celtic People and it is believed that Celts may have migrated from northern Spain (Gallicia) as well as Gaul into Ancietn Britain.

As Britain was a part of the Roman Empire for a good few centuries, people from all over the ROman world probably settled there and intermarried with the British Celts.

Scotland and Ireland and northern Britain were all at one time occupied by Scandinavians during the Viking Age.

That's probably where they got their red hair and light eyes.