For instance, the Greeks established colonies on islands in the Aegean, Ionia, and Sicily, while the Carthaginians later established colonies in Spain and other various regions. Were these colonies State or City-State sponsored ventures with a clear economic or political purpose? Additionally, what was the actual process of colonization like, given that there would presumably be native populations in the colonized areas hostile to foreign colonies. Were these colonization efforts aided by large military forces or did they consist largely of militia's?
I've answered most of these questions previously here. I talked more about the extent to which these settlements were exploited by their mother cities here (short answer: they were not).
The main thing to bear in mind is that the main wave of Greek "colonization" happened at a time when the states of the Greek mainland had seen very little development in terms of state organization or territorial expansion. They were not capable of sustaining standing armies or managing overseas conquests. The word "colonization" is therefore extremely misleading and scholars have tried to introduce new labels for the phenomenon for decades. Overseas settlements were always semi-private ventures to establish autonomous communities, often by forming a symbiotic relationship with existing local populations.