Upon closer inspection, the Nook Tablet reveals a microphone near the headphone jack at the top. It's used to record your voice if you want to make use of the kids' Read and Record books function. You can use it record your kid reading for the first time, or record grandma's own bedtime story for your kid to listen to. The microphone is not enabled for things like Skype, however, unless you root the device. (Not recommended on account of the warranty being voided). Nook Color on the other hand has no microphone.
Another big difference is the Nook Tablet's ability to play sideloaded video at up to 1080p resolution. That means if you have a movie on your microSD card, you can load it on your Nook Tablet and watch it in HD. Netflix videos will only play at 720p on Nook Tablet. For Nook Color, it seems any sideloaded content you play will not be able to achieve 1080p. Also, Netflix is not yet supported on Nook Color, but it may be soon B&N have said. In the video playback category, Nook Tablet also supports more file types (MPEG-4 etc.). Nook Color can only play MP4 or Flash Player formatted videos. Finally, while Nook Color may get Netflix eventually, the app does not come pre-installed. The same thing goes for Pandora and Hulu Plus. Tell us in the comments if you're still torn between which device to get.