Look in stylemojo.css in your skin folder
Note that version numbers only coincide with database changes and official releases of deployment files, ie the version number only changes when we need to run an upgrade script on the database. Lots of other changes and progress happens in the source repository without any change to the version number, so when talking about source code versions it is best to think in terms of the revision number in the repository or the tagged revisions ie we tag the source code as a specific version just before we make a release.
Generally the default branch in our source code repository is intended to be stable so you can and should use the latest version from the repository at any time.