Understanding why some flushing is better than others?

I regularly do multi-color prints. Through some trial and error when slicing, I may play around with the settings to try to save on wasted filament through flushing. Most of the time there is excessive flushing, but in this case I can anyone explain why the red has next to no flushing?

Some info about my print settings first:

It is set to print by object and the mouth is the first item to be printed. This means red is the first filament used, but why does it hardly need to flush much before switching to white for the eyes?

And why does the white and black flush with different values?

Just to be clear, I know why and what flushing is, I am not asking for answers to that. I am asking why sometimes there seems to be a lot of flushing and other times not so much. I also know its related to the colours in that some are darker than others and there are “flush” settings for the AMS based on colours – I am not asking about them, I know how that part works. And this does not hold up in my example though, as this is a dark red changing to white, so you’d expect a lot of flushing.

The only conclusion I can come to is that the printer can calculate the amount of filament to use almost exactly when printing per object but cannot do this when printing by layer. Can anyone provide some insight to this? I want to understand it, so that I can optimise prints more.

I think it’s a simple answer. What if flushing means in their terms using a filament to push another through, in that case the first filament used wouldn’t be a flushing agent so wouldn’t count towards flushed filament.

Is red the first object?

Ah, I see you what you mean. That would make sense given that white is the one with the most flushing/waste - white is the colour right after red.

yes, red is first.