I'm thinking it is not to do with the LED lighting system at all, but rather the crew having fun.
There is a single hard light behind the subjects in all of the related photos i have seen.
The photos are harshly processed in order to bring out the colors more.
The most numerous brand of camera on the station is the Nikon DSLR (IIRC chosen for its radiation protection which was rated better than Canons at the time of selection).
Particular models have a remote commander built in.
Particular strobe units have a remote commander built in.
In both cases these can fire other separate strobes remotely.
In most cases the strobes came with a pack of colored gels with which to make, sometimes fancy, effects.
I know other brands can do this but Nikon had it built in to their system for a while which certainly made it more accessible than if using others, especially at the time that these would have gone up to the station.
For reference, the SSLA LED system is fixed to 3 variations of white light only.
The SSLM does not have any obvious ability to change its colors.
The LED system is fixed in place, sitting in place of where the GLA used to be, and that means it is not likely to be a bright floating source behind the subjects in these photos.
Of course the crew could have brought up their own photographic equipment and accessories to use.
Three pre-determined light settings are envisaged for use in different operational settings. Specifications for Correlated Color Temperature (CCT) and luminance in candelas (cd) settings:
- a General Illumination setting - 4500 K white light, 210 cd.
- a Pre-Sleep setting - 2700 K (blue-depleted) white light, 90 cd or ideally lower.
- a Phase Shift/Alertness setting - 6500 K (blue-enriched) white light, 420 cd.
“While the multi LED system can provide millions of different light spectra, we plan to use three settings for now,”
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=2013
https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=640
Late addition: I found a reference to the pictures by Jack:
https://www.nbcnews.com/mach/science/month-space-pictures-jupiter-s-giant-red-spot-ncsl788416
But no technical explanations though. (They actually just quoted his tweet)