I mean, Tibet was conquered by Chinese dynasties a few times in the past dozen centuries and so it’s been a part of the dominant one on and off over those years, but so have many other parts of China, such as the Taklamakan basin and Sichuan basin as well as their respective surrounding mountain ranges, Mongolia, Eastern Siberia, Yunnan (which used to be the independant kingdom of Dali). That doesnt make Tibet colonized, though. Being conquered does not make you colonized. Colonization implies resource extraction, underdevelopment, replacement of the native population, etc. Being a different ethnicity or belonging to a different cultural region also doesn’t cut it, as China is and has always been multiethnic and multicultural, as have been literally most if not all States from the dawn of civilization itself to basically the 19th century when the romantic ideal of the nation-state pushed European countries to unify their citizens under a single identity linguistic, cultural and ethnic identity, something China hasn’t done.

Edit: Oh yeah, and Communist China having ‘conquered’ Tibet is kind of a huge stretch. Tibet was part of the Qing Dynasty and only became an independant, theocratic, feudal country because of British support. When the Communists tookTibet, the Tibetan serfs thanked them as liberators, not as conquerors. Really, only the Monastic land-owning class was angry about it and fled the area a decade later, not because of any real persecution of the Tibetan people, but because they couldnt stand not being the rulers of the country anymore, much like Cuban gusanos.

Mao took away their serfs!