Tool bar in Safari is suddenly pink

If the restart doesn't help and there is nothing behind Safari, try setting up another admin user account in System Preferences/Users & Groups to see if the same problem continues. Please post back on whether or not this worked. Also try the Safe Mode. Please post back on whether or not this worked.

Isolating an issue by using another user account 

Safe Mode - About

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Etrecheck – System Information

It seems to me like a glitch. Have you tried simply to restart Safari?

The toolbar and the top of a Safari window is semi transparent.

If you have something open behind Safari it could bleed through.

Or a website containing pink colored elements is open and its contents are scrolled "behind" the semi transparent toolbar.