colorCalculator (colorCalculator) {
        if (!arguments.length) {
            return this._colorCalculator || this.getColor;
        }
        this._colorCalculator = colorCalculator;
        return this;
    }
Overrides the color selection algorithm, replacing it with a simple function.

Normally colors will be determined by calling the `colorAccessor` to get a value, and then passing that
value through the `colorScale`.

But sometimes it is difficult to get a color scale to produce the desired effect. The `colorCalculator`
takes the datum and index and returns a color directly.
@memberof ColorMixin
@instance
@param {*} [colorCalculator]
@returns {Function|ColorMixin}