How to change the window color (default: white) in Oneiric? (In Natty, I could do it in
(If 1 doesn't work) How to change the background color in Gedit? (In Natty, by right clicking I could find
profileor something like that.)
The tweakability of Oneiric has suffered due to the switch to gnome 3, so for #2:
gedit supports the themes available in package libgtksourceview2.0-common, and if you are willing to, you can create your own or download a large selection from the net.
Click on Edit/Preferences, on the preferences dialog switch to Fonts & Themes and pick a theme.