The Cygnus constellation contains huge areas of glowing gas, mainly hydrogen and oxygen. The above examples are the most famous ones, because of their conspicuous shapes.
This picture has been created from images taken through two different narrowband filters, which have been asigned to the three colors red, green and blue.
Red = hydrogen alpha emmision line ( 656.3nm)
Green = double ionized oxygen emission lines ( 495.9nm and 500.7nm)
Blue = double ionized oxygen emission lines ( 495.9nm and 500.7nm)