We have a friend who was recently widowed and is living alone.  She has her husbands Colt that she wants to keep in the house for protection.  She's not an experienced shooter and is having trouble with the DA trigger pull.  I'm taking her to a range next week and am bringing several of my 9 MM's for her to try as well.  In the event she can more easily handle a 9, what would the Colt be worth to sell or trade in?
I'd rate it at 80%.

Hard to say with out photos, but $350 or so would be in the ball park.  Could go higher depending on finish or if its one of the scarcer variations.  OP's are fairly common and so far haven't seen the frenzied pricing some other Colts have.

I paid $299 with the NICS and stuff it came to $320 for my OP. But mine is beat because it was poorly stored. It's got some minor pitting and the finish is worn off in areas.

Thanks Guys. I'm taking her to the range next week to seen how she does with it.  May wind up having her sell it and get into something else.

I paid $280 OTD for this one at my LGS about 5 years ago.  

That double action Colt revolver is tried and true and perfect for a new shooter, and home protection. My wife carries a S&W 640. No safeties, no magazines, no de-cockers, no muss, no fuss. Pull the trigger. Boom. Literally. Tell her to keep it and get out and TRAIN with it. The .38 is entirely effective enough for the job. If she decides to sell it, I'm in Arizona, a Colt aficionado and love the Official Police. If a dealer tries to hose her on a trade (they will), email or PM me. H.

Just the First Type Colt Target grips alone now are selling for in excess of $400 and UP.