Preview Edges

Allows you to preview Hard, Shared and Open edges of the model.

Hard Edges

Edges than on both shared faces have different Smoothing Groups.

Shared Edges

Edges than on both shared faces have one or more Smoothing Groups in common.

Open Edges

Edges that only have one face.

The colors selected here are used for as long as you keep PolySmoother opened. If you want to make them the Default colors, you can modify them from the Settings menu.