CSS

To change simple area like the colour of the header text do I have to edit the css files? If so will these changes be overwritten when I update the theme?

Hi,

You can use Child theme, more details here, or use override.css file to add your own rules, which will override existing rules from previously-loaded files.
This is the solution we strongly recommend to implement modifications without altering the default CSS files.

Don't forget to enable override.css file in Advanced Theme settings.
In both cases you don't have to worry about theme updates.