God, this thing is picky. See subject.
Shift-command-C is the default.
I just hit the B key.
It’s a small point, but B not only opens the materials (aka colors) inspector, it also activates the paint bucket tool. Depending on what you are doing that might or might not matter.
As a follow-up…
This is an understandably confusing aspect of SketchUp’s implementation on the Mac: There are actually two independent suites of keyboard shortcuts. One set is built into the menu system when SketchUp is compiled from source. These shortcuts always involve the Command key. They can not be assigned or modified by users.
The second suite is managed by the Preferences->Shortcuts system. Some of these are assigned by default, but all of them can be overridden or modified by the user - with one limitation: because the menu system swallows all command-key chords, whether assigned or not, user shortcuts can’t include the command modifier. The Preferences system therefore won’t let you assign such a keychord.
Where it gets really confusing is that the Preferences->Shortcuts system does not list the menu system’s hard-wired keychords, but does list the commands they target. So, you can innocently (or knowingly) assign your own alternative shortcut to something that is also a menu item with a pre-wired command chord!
I posted a FULL list a while back…
I’ll see if I can find it again…