Version 1.7.4.2 is the latest released version, and it runs on Python 2.7, 3.6, 3.7 and 3.8, with wxPython 4.0.7.post2.
Then you can see the corrections and improvements on CHANGELOG.adoc, for current pre-released version 2.0.b1. This version should run OK, in
Python 3.6, 3.7 and 3.8, with wxPython 4.0.7.post2.
Python 3.9 and wxPython 4.1 were released after this 2.0.b1 version, so I don't recommend them. However, I have been using the current development version (2.0.b2.dev3) that must be installed from the code, as I explain in README.adoc, on Python 3.9 and wxPython 4.1.1.
Depending on what operating system you use, you can try the current development version, see its limitations and known issues.
If you would like to have better control on the colours settings for RIDE, then I recommend to try this version.