Notepad++ is a versatile text editor for Windows. Unfortunately in the current version, some themes do not offer syntax highlighting for R scripts. This can be fixed relatively easily by adding the relevant entry from a theme that does include it. In Windows > Program Files > Notepad++, open the theme that does not work (e.g. vim Dark Blue.xml), and one that does work (e.g. the stylers.model.xml). Simply copy over the relevant bits, and change the colours to match those of your theme.
You might have to start Notepad++ as administrator (right-click on the program entry in the start menu). Let’s hope the next release has this bug fixed…
Didier Ruedin 