Change color of loading page in Safari

When a webpage is loading in Safari, a white screen appears, be it Facebook, Gmail or any other website. If it's contents haven't appeared, then the tab appears completely white (maybe my Internet is way too slow but it takes a few seconds with almost every page, that's why it is annoying). 

Is there a way to override this color so that it appears gray/black until the page is loaded (regardless if the webpage has a white background)?

I am running macOS Mojave 10.14.4. and Safari12.1. I am running dark mode and that doesn't change the color of the loading page.