Menu --> Preferences --> Appearance GTK+
Menu --> Preferences --> Openbox Configuration Manager

hm no.
the windows and buttons are all gray, and inside, for example where are the icons, is white, the start menu too is gray, i want to change this...

Not sure if you can do that with openbox, maybe someone with more expertise can comment.

Take a look in the /usr/share/themes directory. They are GTK+ themes that can be found from numerous sites and other distros. They'll come up in the "GTK+ Appearance" box; just switch to another theme and back to yours to see what your changes look like.

Personally, I've personalised Murrine-Candy and I love it. I've put an archive in my DropBox if you like a bluey desktop: http://dl.dropbox.com/u/6413248/My-Murrine-Candy.tar.gz . Decompress it into ~/.themes/ and it should be in the list after you install the murrine and optionally murrive-svn-themes package(s).

While you can't customise individual items through a point-and-click window, you can copy one of those directories to your /home/(username)/.themes/(theme-name) and edit the theme file. You can see it's quite easy to read if not to work out which bit is which.

You might find the Color Chooser app (gcolor2) to work out which colour is which, and find a nice one.

HIH.

I used a text editor to change colors but a year ago there were and maybe still are editors like http://xyne.archlinux.ca/info/obtheme .