@Simone in my PrusaSlicer configuration I selected GCode flavor: RepRapFirmware, and it looks like in the Custom GCode section it has set Color change GCode to M600. So it may just work.
An alternative is to configure multiple tools in config.g, one for each colour, all using the same heater and extruder. In the tpost0.g file use a M291 command to ask the user "Load filament for Tool 0, press OK when done" and similarly for the other tools. Then slice the model in PrusaSlicer to use a different tool for each colour.