chownではコロンの代わりにドットが使える

man chown

Previous versions of the chown utility used the dot (``.'') character to distinguish the group name.  This has been changed to be a colon (``:'')
     character, so that user and group names may contain the dot character.

Macじゃ無理だけど、CentOSだといけた。

$ chown shigemk2.wheel td.js

Macだとillegal user nameってなる。