Pick Up Objects - Highlight object

Hello!
I have a script for my game that allows me to pick up an object. Currently it says "Can Pick Up Object" when the mouse hovers above the pickup-able object. However, I'd like to get rid of that and make some way for the object to be highlighted if it is pickup-able. Something like turning on a silhouette highlight/outline or a glow to the object. I haven't had any success in doing this with halo objects (that are children of the pick up object). Has anyone succeeded with some kind of highlight method/alternative?

 

googled "unity outline silhouette"

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