[Users] GTK2 Vs. GTK3 Code for Color Labels?

[Dustin Miller]

This is probably a question for developers or users with a reasonable
knowledge of Claws Mail's code.

As I have time, I am trying to trouble-shoot the non-Claws-bug detailed
here (w/ CM v4.1.0 on a couple different Linux Mint 20.3 Xfce systems):
https://www.thewildbeast.co.uk/claws-mail/bugzilla/show_bug.cgi?id=4509
.

So far, my current approach is to just keep trying different themes to
see if I can find one that doesn't show this problem. I will probably
keep doing this unless / until I'm successful or I find a better angle
to troubleshooting this, but so far I haven't been successful.

So my question in this post is to explore a different angle that might
give me helpful information for further research.

What would be the best / easiest way for me to get an idea of how the
Claws Mail code for setting color labels in the message summary view
has changed from the GTK2 versions to the GTK3 port / versions?

I am also interested in finding out more about the difference between
how GTK2 interacts with the message summary view 'object' and how GTK3
interacts with it, but I realize that may be off-topic here.

In case it's helpful for those who are willing / able to reply, I am a
non-coder, but willing to learn new things and not afraid of technical
jargon if it's necessary for clear communication. :)

Thanks,
Dustin