How to Change a Chart’s Style in PowerPoint 2013
Click the chart to select it.
The Ribbon expands to include the three Chart Tools tabs.
Click the Design tab.
The Chart Styles group displays the most commonly used styles for the chart type.
Select the style you want to use from the Chart Styles group.
If the style you want to use isn’t visible in this group, you can click the More button to display a gallery of all available styles. (The More button is the down-arrow button at the bottom of the scroll bar that appears at the right side of the Chart Styles group.)