While working on a project in Xcode, when attempting to take a screenshot, I mistakenly invoked a random keyboard shortcut for some graphic/UI tool, instead of Command + Shift + 4 which I actually wanted to invoke.
It showed the following screen with three tabs (Screenshot, Screen recording and a 3rd item that I can't recall) on top. It also shows a smaller view where a square was shown split into four with some coordinates and colour code at the bottom:
I have tried, but I couldn't reproduce the keyboard shortcut again. What is the tool and what is the exact shortcut? I am using a Late 2013 15" MacBook Pro with US International keyboard, running macOS Mojave 10.14.2.
Note: Kindly notice the two controls highlighted in the screenshot. The top is a tab like interface with three buttons (third one is selected with white background). If you'll notice carefully, the button background is a shade of dark grey which closely matches with Xcode dark interface. Just below that is some kind of UI tool with a box with 4 squares, coordinates and RGB colour codes.