[blincoln]

The "NIRCam Compass" version of the image includes the map of filter to colour that was used.[1] It's not as easy to find, but the documentation for the telescope also includes a complete list of all the filters and what they're used for.[2]

The number in the filter name is (the center wavelength in nanometers) / 10, or (the center wavelength in microns) * 100. An "N" at the end means "narrow" and "W" indicates "wide".

For this image, the team used a pretty straightforward mapping of five filters to more or less the colours of the rainbow in ascending order of filter wavelength, with the shortest wavelength being mapped to purplish-blue and the longest being mapped to orange-red.

When I first got interested in imaging outside the wavelengths we can see, like a lot of people I assumed that the most "accurate" way to represent the data would be to pick three bands in order of descending wavelength and map them to the red, green, and blue channels. That can certainly be a useful approach, but there are often better ways to process the data that make it easier to see things of interest in the result. In particular, doing a R/G/B mapping means that most of the detail in the blue channel is invisible to human eyes, because they're so much less sensitive to blue. TLDR: I think the approach used for this image strikes a nice balance between "intuitive to humans with typical colour vision" and "highlights areas of interest in the image in a useful way".

[1] https://webbtelescope.org/contents/media/images/2023/128/01H...

[2] https://jwst-docs.stsci.edu/jwst-near-infrared-camera/nircam...