Horizontal line color underneath the title text on widget ‘SiteOrigin Editor’

Hi,

Still learning, how can I CSS the horizontal (currently white) line underneath the title text on the widget SiteOrigin Editor?

I have given some of my ‘SiteOrigin Editor widgets’ a ‘class’ that adds a blue bottom border (also added the CSS via WordPress Custom CSS), all okay, I would like the line that sits underneath the title text to match if possible.

Thanks in advance.