What's the Difference Between a Vasal State and a Colony?

A vasal state is not a colony. A colony is a country, or a nation, where a more powerful country comes and indulges in extraction of wealth and treasure. Is the latter a harsher term than the former, as it represents slavery? Slavery lot plunders that india suffered for eight centuries. In this context, are japan, uk, germany, et cetera, vasal states of the us? Or are the pure colonies? Need your opinion.