You need to authorize the Nook Color with your Adobe ID.
If it shows up as a device in ADE, you should be able to do this using menu/Help/Authorize Device (Library/Authorize Device on older more reliable v1.7.2)
If not, you must authorize it using directions from whatever ereader app you are running on the Nook.
If you haven't already authorized your copy of ADE with an Adobe ID, you won't be able to Authorize the device and are a little stuck.
BUT not completely stuck, if you are in that situation ask again before doing anything or you may lose access to that book for ever.