Once you have decided on the initial form of your features—for example, selecting either circles or colors to show population—you can to change their appearance, such as choosing colors, line weights, and transparency. You can create interesting effects by duplicating layers and applying different styles to each layer. In the tip below, you will learn how to create a glowing double ring effect.
When you use proportional circle maps, the large circles may cover small circles, so it may be difficult to view the map details beneath them. Using hollow circles, which are outlines with no fill, helps to solve this problem.
You can also overlap layers using different colors and transparencies to create a glowing double ring effect, as detailed in this tip. Use the provided sample map, or use your own map with layers having numeric values suitable for the Counts and Amounts (Size) drawing style. The sample map includes the original layer (left) plus the copied layers showing the result (right).
Read full article here.