Epson XP-55 driver: how to disable Color Management

You should be able to. If you want to check, click on the Print Settings button in Photoshop's print dialogue to open the Epson driver. Where it says Layout underneath the paper size, choose Printer Settings. As you can see here under Color Mode:, Epson's color management has already been disabled with no way to turn it back on. Which is what you want since Photoshop is already doing the ColorSync chores.

In Photoshop's print dialogue, select "Photoshop Manages Color". Choose your output profile. This automatically bypasses the Epson driver.

Click on the Media & Quality drop down menu and see if there's a choice for color management. Or, if not specifically by that name, see if it's within one of the other headings.

That makes much more sense. Now when you choose to have Photoshop control the color and then check the printer settings, the menu should be grayed out where you see "Color Matching".

Two of our printers have a different reaction to the Apple supplied drivers. For our Lexmark MX410de, it works with the Apple drivers, but there are a lot more features if we install the drivers from Lexmark. The Phaser 7500 is just the opposite. If we use Xerox's drivers, we cannot print to it from Quark XPress. You can see the printer and choose it in the print dialogue within Quark, but the queue never moves. If we download the 7500 drivers from Apple, all of the menu choices are identical, but then it works.

It's possible Photoshop is causing a color management choice to be hidden. Choose to have the printer manage color and see if the print settings choices change.

Also, with some models/brands, the color management dialogue doesn't appear until after you click Print.

I'm wondering if that warning is given as a "blanket statement" or specific to some other setting I may have (e.g. Color Sync).

I'm afraid I can't give you a definitive answer. I downloaded the PDF user manual to look through. It doesn't even mention color management in 120 pages. There doesn't appear to be a way to control it in the Epson driver. Nor does it tell you if the printer has color management at all, or if it's built into the printer with no way to disable it.