With reference to: https://moodle.org/mod/forum/discuss.php?d=346241.

On the page: https://moodle.net/mod/data/view.php?id=28 - there is a link to the Bootswatch site (https://bootswatch.com/) with indications on using the presets there. However the main page is at this time (4th Feb 2017) serving presets for Bootstrap V3.3.7. Boost is a Bootstrap V4 theme. Therefore it would be better to link to the presets designed for V4 instead: https://github.com/thomaspark/bootswatch/tree/gh-pages/4-alpha - because they are more likely to actually work than the V3 versions.