"Advanced" -> "HUD Info" -> "Show Color Under Cursor"
This won't really match... The rendered color depends on the scene lighting, so...
If you are talking about the server version info, the setting is in the Preferences floater, Notifications tab.
It does, but unless you are a Linden, the Admin menu is purposely disabled (menu entry greyed out in the menu bar) since none of the corresponding actions would work for non-Lindens, and some of them would even get you into trouble should you insist on trying to use them (such attempts at using admin tools are logged by LL...).
As specified in the
viewer TOS, support is exclusively provided via this forum.