You might wonder what the X-Ray view mode is for. At first blush, it seems to make everything Gray with White borders. Well, you can do some interesting things in this Mode.
For example, load up the included RTM_First project and set your View-Mode to X-Ray. Now turn on Signals using the context menu. You should see something similar to the next image.
As you can see, the Signals stand out fairly well. But there's more power to X-Ray than just this.
Another useful trick is by Selecting (and then D-Selecting) specific Blocks, you will see those Blocks paint in regular Design-Mode colors. This makes them stand out while all other items literally fade into Gray. See the following Image.
So this allows you to create Snapshots with specific areas standing-out against grayed items. Could be useful in tech Documents or web pages. And yes, this is how Print-Mode works as well though it may only help you viewing Signals.
BTW, you can quickly reset all items back to Gray by right-clicking the View-Mode toolbar button.