To define the color and stroke style for the series and the hover series, use the following code:
seriesStyles: [{
opacity: 0.5, fill: "0-#6aaba7-#5f9996", stroke: "#5f9996", "stroke-width": "1.5"
}],
seriesHoverStyles: [{
opacity: 1, "stroke-width": "2.5"
}]
Notice a larger stroke-width value was used to emphasize the effect of the bar when you hover over it.
