Prototype highlight color. This preference sets the colour of the circle shown behind the Outline view note icons of prototype notes. The default is very light. If prototypes do not show a mark behind them try a darker value for this attribute. To avoid the mark showing, set the value the same as the view's background colour.
The default value is #DDEEDD and it is inherited by the attribute $PrototypeHighlightColor.
See also—notes linking to here: