I just installed Sublime 3, the 64 bit version, on Ubuntu 14.04.
I can't tell the difference between this version and Sublime 2 as far as user interface.
The reason I didn't go with Sublime 2 is that it gives an annoying "GLib critical" error messages.
I wanted to give two tips here with respect to this file in Sublime 3:
You can edit it with pico and use ^W to search the theme name. The first search
result will bring you to an XML style entry where you can change the values. Make a copy
before you experiment.
If you choose the theme in the sublime menu (under Preferences/Color Scheme) before you change this file, then the changes will be cached and your change will not take effect. So delete the cached version and restart sublime for the changes to take effect. The cached version is at
~/.config/sublime-text-3/Cache/Color Scheme - Default/
For Sublime Text 3, all I had to do was add "highlight_line": true to my user settings file: Preferences -> Settings - User. It was only once that preference was set that all the color scheme lineHighlight settings took effect.
Hopefully this will save someone else some of this same flailing about.
If you have SublimeLinter installed, your theme (at least it ST3) may end up in .../Packages/User/SublimeLinter/[ your-chosen-theme ]
As mentioned above - find the nested 'settings' dict and edit or add the 'lineHighlight' entry with your desired #RRGGBB or #RRGGBBAA. I like #0000AA99 when on a black(ish) background.
Handy tool if you do not know your color combinations: RGBtoHEX and HEXtoRGB