The CNN app in the Nook Store shows that it will run on the Nook Tablet and the Nook HD/HD+. Unfortunately the NookColor is not on the list.
The CNN app runs fine on my NC, even if it's not listed as compatible.
Could you describe in more detail exactly what happens when you launch it? Do you get a black screen? An error message? Screen freeze? Does it return to the app list screen? Or can you not download it?