Depends on the logo. If it's just text or a simple shape, it can't be copyrighted.
3Blue1Brown's logo is (probably) copyrightable, but the TED or Veritasium channel logos are (probably) not. If it could be claimed to be derivative of some other work, public domain or not, you may not fully own the copyright either. In general, it can be a big fuzzy grey area that needs a court to decide fully. Meanwhile, a trademark infringement would be easy to show.
3Blue1Brown's logo is (probably) copyrightable, but the TED or Veritasium channel logos are (probably) not. If it could be claimed to be derivative of some other work, public domain or not, you may not fully own the copyright either. In general, it can be a big fuzzy grey area that needs a court to decide fully. Meanwhile, a trademark infringement would be easy to show.