Yes! There is a tiny little freeware/donate ware app that sits in your menu bar called "NightOwl", that not only makes switching from light to dark mode incredibly easy, but also allows you to have some apps stay in light mode despite dark mode being activated. One of these apps is Safari, which is what you want! You can read about it and download it here, the developers site:
https://nightowl.kramser.xyz
I´ve been using NightOwl since Mojave came out, and have had no problems whatsoever! Hope this helps you! Regards, Ian.