This was the quickest fix for me (although I’m leaving out the horizontal blue element altogether):
s->setSliderStyle (Slider::SliderStyle::LinearBarVertical);
s->setColour (Slider::ColourIds::trackColourId, Colours::transparentWhite);
s->setVelocityBasedMode (true);
s->setVelocityModeParameters (0.4, 1, 0.09, false);
You can calibrate the feel of the sliding via the velocity mode parameters.