Over the last day or so, my MacBook Pro was being a little glitchy. I thus decided to reboot it. But when I did, the menu bar was completely transparent (not translucent, transparent) and the Apple icon in the top right was missing.
I could still click where the Apple should have been to access items in that menu (like to access the System Preferences, reboot, etc.), but it just didn’t look right.
If you run into this problem, you might see some recommendations to delete a particular preference file, but I’ve found a simpler solution. Just open the “Desktop & Screen Saver” preference pane and toggle the “Translucent menu bar” setting.
In my case, I didn’t even have to do that much. Just opening that pref pane solved the problem. The menu bar immediately switched from the glitchy transparent look to truly translucent (and the Apple icon returned).