Can we talk about how much of a genius Ishida is for a second?
The prefix re- indicates repetition or withdrawal. Continuations of re- in the context of Tokyo Ghoul could be reborn, reunion, or return. The latter is most likely the meaning Touka had in mind when she named her cafe since she was sure that Kaneki would return to Anteiku. But Ishida also intended re to mean king, which it means in some languages like Italian.
And then there’s the bicolored colon, one of them black and the other one red, just like Kaneki’s eyes. If we consider that Touka included it in her cafe’s name, it’s probably symbolic for Kaneki, as in “This is his place to return.” But with re meaning king, it can also be read as One Eyed King.
So the cafe :re has multiple meanings, similar to the original Anteiku which both meant Antique and peaceful ward, and also referred to the names of Yoshimura’s wife and child, Ukina and Eto.