Make your in-house Gerrit Code Review look like the Google's hosted gerrit-review.googlesource.com, including the icon.
There is nothing to build, just copy the gerrit-bluestyle.html into the Gerrit's /plugins directory. There is no need to restart anything, once the file gets copied, Gerrit will detect after a few moments the new PolyGerrit plugin and will use it transparently.
The Diffy logo and the blue styling is inspired by the official Gerrit Code Review intance managed by Google at gerrit-review.googlesource.com.