I have either lost or misplaced my Nook Color - is there an app I can download that will help me to locate it?
No, unfortunately, to the best of my knowledge, there is no app for the Nook Color that does that.
It's an idea.
I find it helpful to trace my steps backwards from the present moment when trying to locate something.
Was there any identifying information on your Nook that would help someone figure out how to contact you?