TO change the colors of ubuntu ,you need install gnome-color-chooser.

GNOME Color Chooser is a GTK+/GNOME desktop appearance customization tool, to install gnome-color-chooser run below code in terminal

$sudo apt-get install gnome-color-chooser

Features:

• change most important colors (e.g. background, window decoration, tooltips)
• change sizes of widgets (e.g. of buttons, scrollbars or the main padding)
• allow use of light-colored wallpapers without getting icons unreadable
• adjust the size of start menues / panel menues / or large-toolbars

After installation you find that app in System >> Preferences.