I'm using ArcGIS 10.2 Trial and found that there is no Color Ramps. Is it a bug or a restriction?
first make sure that your esri style is enabled.
You can manage the esri installed and your own style files from the style manager.
Go to customize > style manager.
you can drag and drop from any of the esri installed style (just enable it and it will be listed here) into your profile style (see [localdrive]/user/myname/appdata/)
If you are on a Win7 Computer go to:
and either delete or rename the normal.mxt
ArcMap will take a bit longer to open next time (has to recreate that mxt) but the color ramps and styles will reappear.
None of the above worked for me, but then I tried the Repair Option in the Installer and that fixed it finally.