With the staff client refresh, the btn-primary was given a much clearer set of yellow styling.. we should try to add said markup wherever it's missing. This bug servers as a collector.
See doc about buttons in https://getbootstrap.com/docs/4.0/components/buttons/
The staff client is currently on Bootstrap 3.x, so this is what we have to work with now: https://getbootstrap.com/docs/3.3/css/#buttons
Must admit a assumed it t was btn-primary that had been used until I went to fix a case.. at which point I got totally confused... Another one to get added to the guidelines.. how and when to use it