Commanders with at least four colors in their color identity
The four-color commanders in Commander 2016 were a big deal because there weren't any before. (People sometimes use the Nephilim, but they're not actually legendary.) So, there are the five-color ones you already know how to find, and the five from Commander 2016.

It's not too hard to go through all the possibilities to confirm this, but since there's only one result for each query, these searches all currently redirect right to the card:


WUBR
WUBG
WURG
WBRG
UBRG


If someday they print some more, those queries will find them! But don't hold your breath; there's not a lot of design space in four-color cards. Since they're good for commander but not for standard, if they ever do make more, there's a good chance it'd be in a commander set (but not too soon after the current one).