For Macholtz, your post above, its called resonant flourescence:
the green cyanogen CN and diatomic carbon, C2.

dfg



Ioannis wrote:

If I recall right, for nebulae, red usually indicates Hydrogen emissions
and green OIII(?), like in the ring nebula.

What element is responsible for the blue emissions around the Pleiades
or, say, around rho Ophiuchi?

Thanks much in advance.
--
I. N. G. --- http://users.forthnet.gr/ath/jgal/