My first publicly released theme, Follet (the one that powers this site right now), features my also first experiments working with the Customizer. This API offers a great way to see modifications to a theme in real time without actually having to apply those changes to the live site, and a large number of articles have been written about its benefits. What I learned while working on Follet was that sometimes is pretty difficult to manage some styling modifications for the customizable areas of the theme, and I particularly had a really nasty time with colours. However, I think I finally could solve that in an acceptably elegant way.