Ok, first of all, not that important, but anyhow:
Got myself a new macbook pro with touch bar. In safari this shows, when opening a new tab, small icons of my favorites. CircleCI is one of those, but for some reason the icon used is the bleck logo, on a black background. Github for example has a nice white logo, and other sites without settings are showing just a letter of their name.
Using http://realfavicongenerator.net you can easily create the correct tags and image versions to fix this, and even make the favicon retina, which it is not at the moment.