calculateColorDomain () {
        const newDomain = [min(this.data(), this.colorAccessor()),
                           max(this.data(), this.colorAccessor())];
        this._colors.domain(newDomain);
        return this;
    }
Set the domain by determining the min and max values as retrieved by
{@link ColorMixin#colorAccessor .colorAccessor} over the chart's dataset.
@memberof ColorMixin
@instance
@returns {ColorMixin}