New answers tagged photo-management
There's a Mac program called Deep by Ironic Software that will search for colors. It can't find just BW per se, but if you were to select grayscale values it would tend to find images with a lot of grayscale and rank them, so it might get you started. It can do Mac OS tags but can only read keywords, so you might have to do some stuff to get the BW info back ...
I don't know how to do it with Lightroom, but the dead Picasa will help with its Filter By Colors feature. Once installed and your images added to Picasa, go to the search bar and tape color:gray. (image from http://www.addictivetips.com/windows-tips/12-features-of-picasa-that-you-probably-dont-know-about/) Now you can tag all the matching images for ...
You could checkout Mylio for managing you photo library. They have a free tier that's limited in functionality. You need the paid plan (10 USD per month) for "raw support", but if I'm correct that only applies to raw processing. It should still handle all the images as a pair in the free version.
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