This GTK2+ widget theme is intended to be used along with Compiz-Fusion (Beryl) Emerald theme called Neutrino.
The idea is to replace colours in widgets and window borders by other means of design, making prolonged computer work more comfortable and relaxing.
There are two similar GTK themes based on different engines. Both allow colour customization.
For Murrina-Neutrino you may have to install Murrine GTK engine (on Ubuntu it is not installed by default). Check your repository or find it at http://murrine.netsons.org/.
Added pretty similar, but based on ClearLooks engine theme called Neutrino.