Color is great for kids books, magzines and newspapers. I have a Nook Color and like it - but am not sure it was worth the extra money for the Color part.
If you want to be able to get (free) books downloaded from your library, ask there what is easiest to use with their downloading software. If you plan to purchase books, try out downloading from the primary source offering the books you may purchase.
There are a few differences (wt, etc) beyond that, but try to determine ahead of time how you plan to use it and make your choice based on how well the one you want meets your needs.
Sally