As part of the process of getting IDL recognized by GitHub, I had to add IDL support to Pygments, a popular syntax highlighter supporting many languages. This allows generating syntax highlighting of IDL code.

Use pip to install Pygments:

$ pip install Pygments

Then use pygmentize to generate output:

$ pygmentize -O full,style=colorful -f html -o mg_repmat.html mg_repmat.pro

This produces the output below:

Example Pygments output

Here is the full output. This is obviously not perfect (I just wanted GitHub to recognize the language as IDL).