Siemens PPCL: User Defined Language for Notepad++.
The easiest way to install is to use the User Defined Language GUI.
First download the siemens-ppcl-udl.zip file from the releases page.
Extract that zip file - inside will be the XML file siemens-ppcl.xml.
Using the menus in Notepad++, go to Language > Define your language. .. > Import.
Find the siemens-ppcl.xml you extracted and open that.
Close and restart Notepad++. When you open it back up, you should see Siemens PPCL underneath Define your language. Click that and you should see your file highlighted!
I'm not sure that I've come across a global standard extension for these files. I've chosen .ppcl to be the general extension for files in this language. If the file ends with .ppcl, it should automatically be highlighted with the logic in this file. If you prefer a different default extension, it is easy to change in the User Defined Language editor (it's at the top to the right of the Import... and Export buttons).
The color scheme is based on 'londontube.light' from terminal.sexy. I chose this because it uses a pure white background, which most users of Notepad++ will be used to, and I think it looks quite nice.