In the main menu bar go to Help> Excel Help then enter the search term keyboard shortcut. Note that ithe listt may not be 100% accurate due to not being updated since Microsoft made some changes in the name of parity with the Windows version. Also, on laptops/condensed keyboards it may be necessary to include the fn key unless you change the preference for "F" keys in System Settings***.*** If you have any problem don't hesitate to post here in detail.
However, there isn't a keyboard shortcut for the feature you asked about. Neither is the command available for assigning a custom shortcut. If formatting several cells in succession you can use Command+Y to repeat the last action. Perhaps someone can comment on writing a macro [recording won't do it] which can have a shortcut assigned to it.