[Granada]

Is it essential to use filters and/or other specialised equipment (other than a camera, telescope and tripod) to get colours to show up in astrophotos? I've taken quite a few photos and in some photos colours show up (eg Orion nebula) and in others they don't (eg Rosette nebula).
I suspect the trick lies in post-processing, but like I said in some photos the colours don't show up even though I've done everything I can/know in post processing, so I assume I either needed more photos or better knowledge of post processing techniques.