In the long view, all countries were colonised: England was colonised by the Celts, Romans, Anglo-Saxons, and the Normans. Germany was colonised by the Franks, Russia colonised by the Norse, Japan colonised by the Yamato and so on. In many cases, the national identities of the conquered were completely destroyed, or assimilated into the marginalised shadow of the conquerors, or in some cases, lead to discrimination even today (in the cases, of say, the Ainu). That’s certainly not a moral endorsement, but it is a reminder that Japan and Hungary and Poland are technically of the same stripe as more modern “settler-colonialist” states like Israel, the United States, and Canada.
Long story short, there is colonialism every time a new group takes over where someone else was there before and the new rulers try to bring the old inhabitants to heel, and how that is judged is determined usually by nothing less arbitrary than the subjective viewpoints of those viewing it, and whether the conquered people have the “fortune” of being able to survive to a point where their conquerors are able to gain a post-colonial conscience - or when the conquered are able to throw off their oppressors, and write their own narrative.
The seed colonies were settler colonies rather than economic ones or political space-filling. In the Tierran case, the colonies established were mostly trading outposts with little output of their own, which grew into city-states through the fact that ship crews stopped by on their way to somewhere else, liked what they saw, and settled down.