VIncenzo, I’m not entirely clear on what you’re asking for, specifically (e.g., do you need Python code, or would a GUI control work?). Image display was covered in the Aug 5 Delegate Assembly; there’s a summary with video links here:
In the 1st video, around 55:30, Jeff Carlin shows how to change the colormap in Firefly image displays (using the color palette tool). Perhaps that will help.