Increasing colour palette on narrowband image?

I live in a Bortle 9 area and use a L-Extreme filter + OSC camera on nebula targets. The result is increased signal but very red nebula images. I'm wondering if there's a method for increasing the colour gamut of the nebula data to remap the narrow red band onto a broader colour band. I guess giving it false colour, but subtly, and based on the wavelength distribution in the narrow band captured.

Let's say arbitrarily the sky ranges from 1-10 in wavelength; the extreme filter permits capture of only wavelengths 3-4. Can I take the data between 3 and 4 and expand it so it's shown as, say, 2-5? Introducing some blues and greens back into the image, but based on the colour range within the captured narrow band?

I've tried multiple layers in PS with selective colour (creating greener and bluer versions) and overlaying them with low opacity but these seem to recolour the whole image rather than the selective remapping I'm looking for.

There are lots of tutorials for combining multiple narrowband channels captured in monochrome but that's not what I have - I have a single very red image in RGB.

Apologies if this seems articulate- it's difficult to describe what I'm going for. I'll gladly answer questions if that helps get my point across. Thanks in advance !