Portfolio images look highlighted in mobile view

I have about 12 images in one of the sections of my front page hero. Whenever I either go into mobile view using Chrome’s developer tools, or load the page on a smartphone or tablet, the images appear to have a light blue highlight on them, almost like the image is being hovered over. You can see this about a third of the way down the front page, right under “Some Of Our Work”. It probably wont show up that way unless you either use a phone or use developer tools to make the page size that of a smartphone. I can’t figure out what’s causing this…

The page I need help with: [log in to see the link]