IDA, the Interactive Disassembler, is well known tool. It also comes in Freeware version, however, there are several limitations. For example, it is known, that IDA Freeware doesn’t support IDA Python, scripting language which brings the best from the IDA and from the Python world. For scripting, IDA Freeware supports only IDC, a “toy”  C-like language. In past I was wondering if it is possible to run Python even from IDA Freeware, Recently I played little bit more with IDC and I found a way how to pass data from IDA to external Python, and get back results to the IDA.
Few weeks ago, I saw somewhere on the Internet question about IDA Freeware compatibility with the Fluorescence plugin. And because this plugin is written in IDAPython and IDAPython isn’t officially supported by IDA Freeware, also this plugin isn’t compatible. However, when I checked what this plugin does, it turns out that it is very simple - its purpose is to highlight call instructions. So as an exercise I re-created IDC script with similar feature, and moreover, I also created plugin version of IDC Fluorescence.