List all tags in Terminal in Mavericks?

The tags name are in ~/Library/Preferences/com.apple.finder.list.

You can read it with

defaults read com.apple.finder.plist ViewSettingsDictionary

It will need some parsing to be a bit clearer :

defaults read com.apple.finder.plist ViewSettingsDictionary | 
    awk 'NR%12==2'| grep -o '".*"' |  sed 's/^.\(.*\).\{18\}$/\1/'

Other possibility is parsing the plist as xml. To do that you'll need to first convert the plist from binary to xml using.

plutil -convert xml1 ~/Library/Preferences/com.apple.finder.plist

You can also use tag:

tag -tgf \*|grep '^    '|cut -c5-|sort -u

tag -f \* finds all files with tags, -t includes tag names in the output, and -g prints each tag on a separate line.