issue happens in GIMP 2.6.8 (it looks like gtk+ tries to emulate the windows native colors, but seems like the menu is still a fake menu, not a native windows menu)
does not happen in inkscape 0.47 (still gtk+ has "fake" menus, but with a different color scheme)
also does not happen in seq24 (using gtkmm - there it has even different menu type)
here windows7 x64:
issue happens in GIMP 2.6.8 (it looks like gtk+ tries to emulate the windows native colors, but seems like the menu is still a fake menu, not a native windows menu)
does not happen in inkscape 0.47 (still gtk+ has "fake" menus, but with a different color scheme)
also does not happen in seq24 (using gtkmm - there it has even different menu type)