takes time to switch from one color to another
Does this mean the time to pause and switch, or the time for the remaining filament in the nozzle to clear out? I think the latter, although I could not see the side of the Iris box too well. If this is the case:

Maybe a remote single layer object could be modeled, with no support (does not touch bp), such that it occurs at the same Z height as the change-in-color requirement. This way, when the nozzle reaches the layer where it needs to change color (and if you are watching it), you will see it move way over to the remote object for the first time. Pause it then, and change filament.