I haven't tried it but I would imagine colloidal silver would be easy to incorporate, the problem is I'm not sure what the lye would do to it. As I understand it sodium hydroxide precipitates silver oxide causing it to come out of solution and looks pretty icky. I don't know the chemistry behind colloidal silver, I do know the molecules are small but how that would be affected I'm not sure. You could always do a test batch and find out.