excludedColor (excludedColor) {
        if (!arguments.length) {
            return this._excludedColor;
        }
        this._excludedColor = excludedColor;
        return this;
    }
Set or get color for symbols excluded from this chart's filter. If null, no
special color is applied for symbols based on their filter status.
@param {Number} [excludedColor=null]
@returns {Number|ScatterPlot}