I've seen this.
I experienced occasional intermittent fuel pressure drops, typically when descending from higher than usual altitudes (ie. pulling back on the throttle) and often when flying over or near water (probably coincidence, but sure gets your attention). Would fall into yellow range, and sometimes drop into the red for a few seconds. I blamed summer car gas fuel blends and even replaced the Kavlico pressure sensor at one point. Seemed to go away for a while but would still happen from time to time. Could not figure it out and admittedly became complacent.
But after replacing both the Rotax engine driven fuel pump and the Facet pump at the 5 year point my fuel pressure indication was noticeably higher in cruise. I haven't seen fluctuations occur now for several years. Very likely was a failing Rotax pump that I should have replaced years earlier. Lesson learned.