You can customize the look of an object by adding a border, shadow, or reflection. You can also change the opacity (transparency) of some objects. The style options available depend on the type of object that’s selected.
You can add a border, such as a picture frame or a dotted line, around an image, video, shape (including lines), or text box, then modify the border’s thickness, color, and other attributes. You can also add a simple outline around a chart.
Select a shape, image, video, text box, or chart.
In the Format 
sidebar on the right, do one of the following:
For shapes, images, videos, or text boxes: Click the Style tab.
For charts: Click the Chart tab.
Select the checkbox next to Border, then use the tools that appear to achieve the look you want.
Note: If the object is a chart, the border is a simple outline that can’t be customized.
You can add a shadow to images, videos, shapes, text boxes, and the data in charts.
Select a shape, image, video, text box, or chart.
In the Format sidebar on the right, do one of the following:
For shapes, images, videos, or text boxes: Click the Style tab.
For charts: Click the Chart tab.
Select the checkbox next to Shadow, then use the tools that appear to achieve the look you want.
You can create interesting effects by making some objects (images, videos, shapes, and text boxes) more or less see-through (opaque). When you put a low-opacity object on top of another object, for example, the bottom object shows through.
Tip: You can also change the color of shadows, borders, text, and more; whenever you see a color well in the sidebar, click it to choose a new color for the effect or selected text or object.