This tutorial shows how to add syntax highlighting for GCode files (NC, Gcode or G files) in Notepad++. This was one of the user's question. Gcode files are computer aided machine programming language used for CNC machines (Milling, Lathe etc).
Here is the link to Gcode color syntax highlighting for for editing Gcode in Notepad++.
https://raw.githubusercontent.com/robEllenberg/gcode-syntax/master/gcode.xml