Based on Linux Mint's default theme, Mint-X, and inspired by the GTK2 theme Mint-Metal-X-Blue, but made for GTK3/Cinnamon, I give you Mint-X-Colours. I find the green to be suboptimal, so I swapped it out with blue, red, and purple. Looks great with Faenza Cupertino icons.
To install, extract to ~/.themes/
Also included, a Red version for your root user, so that applications being used as root will have red controls / highlights. To install, extract the file from Mint-X-Blue-ROOT, then move it to /root/.themes/
sudo mv Mint-X-Blue/ /root/.themes/Mint-X-Blue/
The red theme attempts to load the icon set Faenza-Cupertino, if you use a different icon set edit index.theme to point to your set.
Finally, if you want to simply use the red/purple theme for your normal user, download Mint-X-Red or Mint-X-Purple. Extract to ~/.themes/ to install, or /usr/share/themes/ so that they will be available to all users - including when you launch applications as root.
2012-02-20: Fixed info box colour (like in Nautilus/Nemo search)