Although there was certainly a variation between the generally dark haired Iberians and the taller, blonde or red-headed Celts, both types may be seen in the northwest today, and have quite easily identified features which differ both from the Spanish of the Eastern ports, and the Andalucians, which show considerable Moorish influence.
Today's Galician or Asturian, as well as the people of Northern Portugal, show that the Celti-Iberians, as they became known, have produced many descendants who occupy these regions today.
But did these earliest people call themselves Celts? As we have already seen, there is some conjecture that they called themselves Iber, and that the land of Iberia, today's Spain (which comes from Hispania, the name given to the Peninsula by the Romans), and subsequently Hibernia as the ancient land of Ireland, the Land of Ir, or of Erin.
While he may not have been the first, Herodotus mentions the Keltoi. They are also called this and Galatai by other writers of the period and later, and it is interesting that the two names are given to essentially the same peoples. They are generally described as having fair or red hair, and blue eyes. But the same description has been attributed to the peoples of Scythia. The Romans modified this to the Celtae and the Galli. But although there were to be found throughout Europe and as far as the Black Sea, the Celts as a people do not seem to have existed. They were instead a great number of tribes who appeared to have acted, for the most part, independently of one another. There was no Celtic Emperor, nor common leader. They had no central administration, no form of government outside of what was determined individually by the tribes. They had no unified army which could be called upon in times of war against a common foe. Perhaps because the European Celts, such as they were, had no common foe.
The problem of identifying who, in fact were "Celtic" and who were not and the extent of Celtic culture might be solved if we were more knowledgeable as to which of the tribes identified by the Greeks and the Romans were indigenous and which were not. This is particularly true in the Iberian Peninsula. Speaking of the Keltoi of Iberia, Herodotus identified them in a region close to the Algarve in southern Portugal, yet Aristotle claims they were above Iberia in a very cold region. Although the northwest is colder than Portugal, even during the winter, it could hardly be described as very cold - very wet, maybe. The interior of Castilla, however, can be downright chilly in the winter.
It would appear that there is little agreement. The problem as it appears to me is that we have fallen into a tendency to think of the Celts as a clearly identifiable people, and I think I have demonstrated that this was not so. Although the term "Celtic" may mean certain common features in terms of economics, social structure, and religion, even this differs from area to area, and likewise, since geography frequently determines character, from tribe to tribe. Only language seems to be a constant factor and it remains so today, although by this criterion - and this has kept Galicia from being accepted by the Celtic League - the so-called Celtic peoples remaining in Galicia and Asturias, are not so by contemporary definition.
Besides, the time of Herodotus is much later than our story, so next time perhaps it is time to return to it.
I've just discovered this very in depth article about the Celts in Iberia so thought I would share: