Bluebird was the default theme for Xubuntu 10.10 but since 2011, Greybird has been Xubuntu's default theme. As its name indicates, Bluebird is a blue theme. The Shimmer Project are the designers and developers of both Bluebird and Greybird.

Although originally created for Xfce, Bluebird also supports other GTK+-based environments including Cinnamon, GNOME Shell, MATE, and Unity.