Large scope owners routinely mentions seeing a pink tinge to M42, along with green. I'd have to agree with this having seen the pink through my 17.5". Green I've seen in all my scopes, from my 2" to 'Odessius'.
I haven't seen M57, so I can't say.
Another planetary with a distinct blue colour is "The Blue Planetary" nebula NGC 3918 in Centaurus. It is a very vivid blue colour, and a bit of magnification, 100X +, will give the disk some size.
I'll have a go at 3242 this weekend.
What unnerved me though was The Rosette Nebula. I was finally able to nail this big bugger last new moon, and with an OIII filter. What I saw was it glowing with a violet colour!
I was using my 17.5" f/4.5 scope with an RKE 28mm and the OIII filter.
Colour is a very difficult thing for our eyes with DSOs. Not only are these objects dim, but also in the mix is colour blindness, not just age. What is worst is 2/3 of all males are colour blind, from very, very mild through to no colour perception (very rare). And the wavelengths DSOs glow at, nebulae in this case, our eyes are least sensitive to, red and blue.
