Why does my site see a background that contrasts with the site's main background when viewed on safari on a Mac?

Question

safari

On the site , the main background color is #0a0c19. The customer says that when viewed on a safari on a poppy, some background is visible in addition to the main one (the color is slightly lighter than the main one), when viewed on other browsers, everything is fine.
Here is a description of the problem from the customer himself.
I can’t solve the problem myself, I don’t have a poppy, look, if it’s not difficult, where does this foreign background come from?