Spectrum is a theme for the static site generator Hugo, the CSS framework Bulma makes it completely responsive and in combination with the lookup order of Hugo templates it can be easily personalized.
This very site is an example of the Spectrum theme, by default it won’t look like this but more like that.
To customize the theme you must override one or more Bulma variables; create a
bulma-variables.sass file in your
<site_root>/assets/css folder and set any of the variables found on the official Bulma documentation.
It’s also possible to add custom CSS, to style any custom layout you might want to create; to do so create a
personal.sass file in the same folder and put everything in there, all Bulma variables will be available but overriding them won’t work.