I want to pick a color from screen using the DigitalColor Meter. However, I cannot seem to lock the mouse. How am I supposed to use this tool?
Once the DigitalColor Meter is running, you can pick a color on the current mouse position by using the shortcut:
⇧ + ⌘ + C
It will store the value in the clipboard. The standard is RGB values e.g. 255 255 255
If you prefer hexadecimal notation, you can check this answer.