Here’s a humble attempt to reprocessing the Crescent I did with Gustaaf Prins and (waiting for clearance to disclose name). It’s a composition of red, green, blue, Ha, SII and OIII channels.
Of course when performing this kind of processing, there is usually no pretense of achieving real natural colors. The problems lies mostly in two factors: first, the Ha and SII channels are both reddish, while the OIII channel is greenish blue; second, the intensity of the signal at different bandwidths varies considerably, and if you don’t want to end up with a very color-unbalanced imaged, you need to stretch different channels differently.
This image uses red, Ha and SII (mixed in different percentages) for the red channel, green and OIII for the green channel, and blue, OIII and a pinch of Ha for the blue channel.