How to acquire the frame colour?

[RokeJulianLockhart]

As explained at discuss.kde.org/t/34069:

Rationale

I'm implementing a line number area with QPen in a QPlainTextEdit. Undermentioned, you can see the line in question set to Accent:

I want to utilise the semantic colour for its separator, rather than apply #BBBDBE:

PyQt6.QtGui.QPen().setColor(PyQt6.QtGui.QColor(PyQt6.QtWidgets.QApplication.palette().color(PyQt6.QtGui.QPalette.ColorRole.Button)))

(I suppose I could use a QSplitter, but I don't want to refactor the widget yet.)

Questions

Consequently:

1. What colour from the QPalette (as KColorScheme exposes from the applied .colors file) does the QStyle use for the QScrollBar's QSplitter?

2. What opacity is it?

...or, better yet, how could I determine this myself, in the future? I ask because:

1. None of the undermentioned appear appropriate:

   class QPalette(PyQt6.sip.simplewrapper):
   
       class ColorRole(enum.Enum):
           WindowText = ...
           Button = ...
           Light = ...
           Midlight = ...
           Dark = ...
           Mid = ...
           Text = ...
           BrightText = ...
           ButtonText = ...
           Base = ...
           Window = ...
           Shadow = ...
           Highlight = ...
           HighlightedText = ...
           Link = ...
           LinkVisited = ...
           AlternateBase = ...
           ToolTipBase = ...
           ToolTipText = ...
           PlaceholderText = ...
           Accent = ...
           NoRole = ...
           NColorRoles = ...
   

2. ...and I do not know what to look for in invent.kde.org/plasma/breeze/-/tree/9f6f7eb6f2bf61b66f0712e5975c5ed6ba2465f3/kstyle.

Unfortunately, I'm beginning to believe, due to the comments under stackoverflow.com/questions/63915157, that this might not be feasible, even if technically possible (which is also doubtful). Can anyone confirm either way?