public int getPreviewColor() {
        return previewChartRenderer.getPreviewColor();
    }
Preview chart that can be used as overview for other LineChart. When you change Viewport of this chart, visible area
of other chart will change. For that you need also to use
{@link Chart#setViewportChangeListener(lecho.lib.hellocharts.listener.ViewportChangeListener)}

@author Leszek Wach
hellocharts-library/src/lecho/lib/hellocharts/view/PreviewLineChartView.java