I need to change the font and colour of the titles of my albums. Where can I edit this? I currently have the zpBootstrap theme installed. Is it a default part of the theme? Can I install a plugin to edit this?

You need to modify the theme's CSS.

hi
to change the main bootstrap css rules, you can create your own css compiled files.

to do that, load the file config.json provided in directory /_bootstrap_3.4.0\bootstrap-compiledof the theme in
https://getbootstrap.com/docs/3.4/customize/.
then, edit the rules as you need.
then, you have to replace bootstrap*.* in directory /css with the new compiled files.

you can also change specific css values (not bootstrap ones) in /css/zpBootstrap.css.