Here is a colour image with NII mapped to red and HA to green. There is a bit of difference in these emissions but it is subtle.
Full res image 7MB
http://d1355990.i49.quadrahosting.co...188_NII&HA.jpg
The emission of NII only occurs due to the presence of very hot blue stars. This will vary from object to object. A 5nm NB filter or wider will collect both NII and HA.
Bert