How Do I Do That in Photoshop?

Change the Color Outside My Image Area?

If you want to change the color of the workspace background outside your image, just Right-click anywhere outside your image (if you’re using Application Frame with tabbed documents, you may need to shrink your image view a bit [zoom out]; if not, click-and-drag out your image window, so you can see the canvas area), and a pop-up menu will appear with choices. Choose the one you want and you’re good to go.