This post is a quick general Autocad tip as I recently discovered the built in SETBYLAYER command while looking for a LISP routine to change a selection set of entities color to ByLayer.

The SETBYLAYER command changes property and ByBlock settings for selected objects to ByLayer.

This command is a great cleanup tool if you have a drawing with a lot of entities that someone has set the color to a specific color rather than bylayer.