I don't know if these issues are really connected; I only know that they seem 
to occur together. Feel free to separate the two issues if that is more 
accurate. 

Issue #1
I noticed that my system colors are not applied to some applications. In 
particular, the Firefox/Iceweasel and Seamonkey browsers. Sometimes when I 
start up, these take on my KDE4 Plasma color settings (even when KDE4 is not 
installed); sometimes (maybe one-third to one-half of my installations), 
everything in the GUI is white, sort of like in Gnome desktops that I've 
seen. (Again, Gnome is not installed, though I do use some standalone 
applications.) I can make PaleMoon take on my TDE color scheme settings, and 
when I uncheck the button that says "apply to non TDE applications", etc., 
it, too, turns all white like these other apps; however, PaleMoon never takes 
on the color scheme from the KDE4 Plasma desktop. And then, at other times, 
after I install I get my TDE settings. (Maybe one out of ten installations, I 
will have Seamonkey and Firefox/Iceweasel use my TDE color scheme settings.) 
Then again, sometimes they will use my KDE4 settings. Both are available in 
my TDE desktop, but only KDE4 settings are available in that desktop. 

TDE
Trinity Control Center/Colors
x Apply colors to non-TDE applications

KDE4
System Settings/Application Appearance/Colors/Options
x Apply colors to non-KDE4 applications

I don't so much care if they use the KDE4 settings or the TDE color settings, 
just so long as it's not white. This isn't just that I hate that my pretty 
desktop is spoiled; I started using these settings because a white screen 
triggers a migraine - especially when I am working late at night in a dark 
room. I impose dark screen settings on my default browsers and other 
applications, too, for this reason. Also, there is a practical reason: 
whenever I see a white screen, this usually reminds me that I have opened 
that application as root, so that I am sure to be careful I don't really mess 
up or delete stuff. 

It occurred to me to try to purge the offending applications, then to try to 
reinstall them from within the KDE4 desktop environment, and to do the same 
within TDE, but this made no difference. Thus far, my only options are either 
to live with the lack of color, or to reinstall my system yet again, and hope 
for the best. 

Issue #2
This may or may not be related; it could be a permissions problem. I now find 
that some of my external hard drives cannot be mounted or used, because I can 
only access them as root. Even if I wanted to use them as root, it means that 
I cannot access music files with my media player, for example. Again, this 
has happened before, though not often, usually after a fresh installation. In 
the past, it seems the only cure is to reinstall everything. However, since 
I've not got this Devuan Jessie system working pretty well, I don't want to 
mess up a good thing, especially if there is an easy fix. 

I've already tried changing permissions, and that sort of thing. I am guessing 
that there might be some kind of config files buried somewhere. I've 
searched, but thus far I can find nothing. 

Bill

Devuan Jessie 8.8.x 
TDE Trinity 14.0.4