It means whatever you think of when you say it.
To some people white hat means purely content marketing in the hope of getting some backlinks, to some people it means not even thinking about "link building". To some people it means only building the best quality links. To some people it means only doing guest post outreach. To some people it means having complete control of all external links.
Black hat has just as many interpretations.
Blue hat, never heard of it but sounds like it's probably got just as many meanings as well.