[Users] How to change the background color on the folder list and message list?

[slitt at troubleshooters.com]

>On Sun, 17 Jul 2022 21:16:05 -0400
>slitt at troubleshooters.com wrote: 
>
>> Is there something I'm missing, or do I modify that background color
>> completely outside the theme?  
>
>You haven't understood what Brad said. Change the GTK theme - this is
>not the icon theme in claws-mail, this is the theme used by GTK
>applications on your system.
>
>with regards
>
>Paul

Thanks Paul,

So I went into Openbox Configuration Manager and changed the theme
first to Clearlooks-Olive, then Natura, then Orang, but the background
color of current message highlight and current folder highlight
remained dark blue after quitting and restarting Claws. I used
gtk-theme-config and changed the color of every background color,
restarted Claws, and still dark blue.

I then went into /home/user/slitt/.config/gtk-3.0 to edit gtk.css,
verified that @menu_bk_color was not dark blue, and noted that almost
all menu/scrolling type backgrounds were set to menu_bg_color. My
current /home/user/slitt/.config/gtk-3.0/gtk.css can be seen at: 

http://sprunge.us/RrnuOv

My Claws-Mail 4.10 appears to be using GTk 3, as shown by the
help-about screen:

===================================
System Information
GTK 3.24.34 / GLib 2.72.2
Locale: en_US.UTF-8 (charset: UTF-8)
Operating System: Linux 5.18.11_1 (x86_64)
===================================

So I need to know what theme attribute Claws uses for the highlight on
the current email in the email list and current folder in the folder
list, and what file to edit to access that attribute.

Thanks,

SteveT