How to change default product image on Refresh theme?

[theengravers]

Our store displays the first image for a product on the collection page, but when you click on a product, the page automatically displays the second image. Once a variant is selected, it shows that image.  We'd like the page to display the first image (the same thing shown on the collection page), but still have the image change once a variant is selected.  I've tried other solutions from the community here, but I haven't been able to find one that does both of these things.  We are using the Refresh theme, if that helps.

[theengravers]

What am I looking for in terms of the product page template? There are multiple .css and .json files that it could be.  And once I'm in the correct place, what kind of code might be responsible for determining which image is displayed?