Thanks for a quick reply. Are you sure about the Highlight color though? What you say makes sense, but this is what the QT documentation says about it (and what maybe misled me):
A color to indicate a selected item or the current item. By default, the highlight color is Qt::darkBlue.

Could this be a discrepancy in definition between GTK and QT?

The only possible symbol that could represent the active text you mention is QPalette::BrightText. But it is of grayish white in your themes and probably pure white for the Digital Nature one. I'm pretty much clueless. It could be a bug in QT that this color doesn't get set properly...

The QPalette::BrightText description is as follows:
A text color that is very different from WindowText, and contrasts well with e.g. Dark. Typically used for text that needs to be drawn where Text or WindowText would give poor contrast, such as on pressed push buttons. Note that text colors can be used for things other than just words; text colors are usually used for text, but it's quite common to use the text color roles for lines, icons, etc.

If you have any more ideas, please tell me... I'll stop OTing in your thread and search elsewhere once again, thanks.