There has been some discussions about this reddish tail on Cloudy Nights.
https://www.cloudynights.com/topic/716780-comet-neowise-high-resolution-spectrum/?p=10332533
I wondered about sodium but the neutral sodium tail seen with Hale Bopp fell between the dust and ion tails rather than at a larger angle as here. I am wondering if it could be from NH2, the emission bands of which fall in the red region of the spectrum. Perhaps some mechanism separating ions by molecular weight, CN, C2 being heavier ?
Robin