QtGui.QColor.NameFormat.HexArgb?

Does it work to just set

try:
    re.compile(text)
    self.ui.exampleFilter.setStyleSheet('')
except:
    colors = DarkThemeColors if app.property('darkMode') else LightThemeColors
    qcol = QtGui.QColor(colors.Red)
    qcol.setAlpha(100)
    hexcol = qcol.name(QtGui.QColor.NameFormat.HexArgb)
    self.ui.exampleFilter.setStyleSheet(f'background: {hexcol})
    return

?
Going through mkColor twice just to prefix #64 to the string seems like the long way around.

And I think clearing the stylesheet should revert to the original colors, without explicitly setting one. Did not test, though.

@NilsNemitz beat me to it, but yeah, get the colors via accessing DarkThemeColors or LightThemeColors based on the darkMode property.

Since the colors come in string form, I don't think we should even convert to qcolor.

colors = DarkThemeColors if app.property('darkMode') else LightThemeColors
red = colors.Red
self.ui.exampleFilter.setStyleSheet(f'background : {red}00')

Qt's stylesheet seems to be AARRGGBB, though. Not sure if
self.ui.exampleFilter.setStyleSheet(f'background : #64{red[1:]}')
is more readable than the detour through QColor.
:)

Actually, alpha through hex codes seems to be unspecified:
https://doc.qt.io/qt-5/stylesheet-reference.html
background : rgba(r, g, b, a) seems to be the documented way to do this.

oh yeah, rgba() is likely far more readable

colors = DarkThemeColors if app.property('darkMode') else LightThemeColors
error_color = pg.mkColor(colors.Red)
self.ui.exampleFilter.setStyleSheet(f'background : rgba({error_color.red()}, {error_color.green()}, {error_color.blue(), {error_color.alpha()})