You can add shadow effects by increasing the value of the Offset property. The shadow is more noticeable at values from 3 to 5 (the highest). You can darken your shadow by increasing the transparency. The default value for the transparency is 64. The shadow effects on the element can appear softer if you enable the soft property.
For more information on applying the shadow effects to a specific chart element, see Add a Shadow to the Chart Header and Footer.