Creating a molding around a selected target

Well, im tryng to put some effect into my monsters when they are selected, something like that:

When the monster is not selected:

When the monster is selected:

Im not asking how to do that in code, because i know, i just dont know how to create this red molding around the monster, it is a 3d game.

Try using a custom GUI texture

http://wiki.unity3d.com/index.php?title=Silhouette-Outlined_Diffuse

This one is even better: (doesn’t have overlap problems)
http://forum.unity3d.com/threads/96005-Trying-to-make-a-silhouette-outline-shader/page2