Since ProPhoto 6 does not yet have search appearance customization we have made a workaround by utilizing CSS which you can change in a few easy steps.
First, navigate to your Search Page template in the Customizer area, and click the cog next to Site to open up the page hierarchy. Go to the Advanced section to edit the CSS
We have also coded in the search customizations for the Blog with Sidebar page template. You will need to go to the template and in the Main Block sidebar column, click the cog to bring up the customizer. Go all the way to the end and in the SASS area make your changes.
If there is something that is not clear or was not covered, please submit a ticket and let us know.