I'm using the KDE desktop (but originally installed normal Ubuntu). I like dark colors for my desktop theme. The only dark theme I see installed by default is "Elegance". When I select this theme, the default colors for text areas is light text on a dark background. This is just fine when both get set, but some places don't seem to use the dark background. For example, text fields in Firefox are mostly still white background, but the system light foreground is being used. AskUbuntu itself suffers this, in the "Tags" field as I type this question. Buttons and text areas on some of the system menus and dialogs likewise become unreadable. See screenshot for an example, trying to add a widget to the bottom panel (see the upper left corner).
Is there a way to correct this color? I don't see any method in the System Settings->Workspace Appearance->Desktop Theme dialog to customize any of the colors.
I found a post with the same problem ( https://forum.kde.org/viewtopic.php?f=67&t=106925 ), and it's marked "solved", but it looked like the solution was "stop using the Elegance theme".