I don't have any direct info for you but I recently had a fascinating conversation with a gentleman about using old B/W photos for historical color research. Basically, different colors will show up lighter or darker based on what kind of film was used, light incidence angle, etc. It's quite complex.
Unfortunately I can't remember his name but he is working with Eric et al. on Coach 9; maybe Eric can chime in.
I've used those colorize apps before. They aren't actually extracting any information from the photo itself; the app is just guessing based on what it's seen in photos of similar composition. So don't put too much stock in the results.