Spree Blue Theme is a standalone theme for Spree Commerce version 0.70.0 or later.
Add the following line to your Gemfile:
gem 'spree_blue_theme', :git => 'git://github.com/spree/spree_blue_theme.git'
NOTE: It's important that you add this line at the bottom of the Gemfile, or at least AFTER any other extension/engine/gem that you'd like to theme (i.e. Spree)
$ bundle install
Optional: Clear out precompiled assets (required for install in sandbox):
$ bundle exec rake assets:clean