Things I have tried
I’ve turned off themes, and by putting in a CSS snippet h6{color:red;}, I have found that the offending CSS is over-riding CSS snippets as well.
What I’m trying to do
In my preview mode, I have H6 headings showing up in a grey font colour. I remember writing the CSS for this, but now cannot find where this CSS edit has been made. It is not in snippets or a theme.