This image is composed of NII and HA data.
NII to red
NII+HA to green
HA to blue
Large image here 11MB
http://d1355990.i49.quadrahosting.co...5/6188_NAH.jpg
I upped the saturation to accentuate the differences between NII and HA.
If you have a look around there are some red and blue stars.
Below is a picture of two PN's one is obviously much brighter in NII.
Bert