Safari URL bar discoloration

In Safari (12.0.3 and probably earlier) the URL bar can have an element of discoloration. I think is partially driven by the content/colors of the page being displayed as the amount of discoloration changes from page to page and appears to be stronger for pages that have darker colors below the section that is discolored.

Unfortunately this discoloration can mimic the symptoms of macula degeneration if you are glancing at this spot on the screen. As such I want to get rid of it.

How can I turn this discoloration off?

System Prefs > Accessibility > Display > Reduce Transparency.

You can search it with 'reduce'.