From my highly light polluted porch (chicago suburbs), the nebula
appears very clearly green.

My experience as well. The other night it was particularly green.

Try this one one for size. Best to do this when the moon is near full because
it involves ruining your dark adaption.

A scope of at least 10 inch preferable:

Step #`1. Find Orion Nebula

Step #2. Stare at the moon with your observing eye through the scope or a
bright light for long enough to be sure that you dark adaptation is gone and
that you are relying on your color vision.

Step #3. Find the Orion Nebula with your other eye and then view it with your
"observing eye" (not dark adapted) eye with a low power eyepiece.

What I seem to see doing this is a smaller but more colorful Orion Nebula.

My hypothesis is that since night vision is essentially greyscale, by bleaching
out the receptors, that greyscale signal no longer overwhelms the color signal
from the cones and if the image is bright enough (low power, large exit pupil)
then one can see the color....

For what its worth...

jon isaacs