I've added the following to my gtkrc file(which i've downloaded from art.gnome.org)
style "titlebar" = "flat"
{
  # Normal base color
  bg[NORMAL]  = "#bbbbbb"

  # Unfocused title background color
  bg[INSENSITIVE]  = { 0.8, 0.8, 0.8 }

  # Unfocused title text color
  fg[INSENSITIVE]  = { 1.55, 1.55, 1.55 }

  # Focused icon color
  fg[NORMAL]  = { 0.2, 0.2, 0.2 }

  # Focused title background color
  bg[SELECTED]  = "#4A4A4A"

  # Focused title text color
  fg[SELECTED]  = "#F9F9F9"
}

widget "title_bar" style "titlebar"

And I put this in my python code:

MenuBar.set_name("title_bar")