We may be entering definitional land, as with the debate on fascism, and maybe colonialism is too multi-faceted in meanings to bother using, but I think its worthwhile to distinguish it from settlement, genocide and the other measures benefitting the West.
Colonialism was a specific mechanism for dominating another nation from a minority position, as with the British Raj or other economic mechanisms to extract an economic surplus from the dominated population to the advantage of the colonial state. ______________________________________________________
If any variant of imperialism has the right to be titled "colonialism" then surely it must be that form of imperialism based on settlement. One implants a colony, after all, by allowing colonists to settle on a territory. Pick up India Office documents, in contrast, and try to find any official reference to India as a "colony". It will be a long search.
Michael McIntyre