Mysterious blue color showing up on my responsive menu is slowly driving me insane. HELP!


I know I'm going into 3rd-party territory here, so I don't know if anyone can help here. But I can't seem to figure out why something's happening on a site I've built, and I'm hoping someone somewhere has a solution -- so I'm asking for help wherever I can.

I added the "Responsive Menu" plugin to the following site:
It adds the "hamburger menu" for mobile devices, and I've used it before with no problem. This time I've set it for ALL screen sizes, and it's a one-page-only site (important). The problem is that once you click the hamburger icon (on Safari for Mac only), it turns part of it blue (sometime you need to click a link, or close it to see the blue appear).

I assumed this might have something to so with the ":active" or ":visited" states of elements at play, since this is a one-page site, so I tried to fix it with CSS. BUT -- I've tried nearly everything, every single combination of elements, selectors, variables, etc. that I could think of. I used "!important" each time, and cleared the browser before each attempt. No luck with anything -- nothing works!!

To make it more confusing, this seems to ONLY be happening on desktop Safari on a Mac. The blue doesn't show up on Chrome, Firefox, or even mobile Safari and PC Safari. Any ideas what's happening here, and how I can get rid of the blue (on click) with desktop Safari?? I'm going crazy!!
Thanks in advance.