Like for example, this image shows that with only 4 colors and different combinations of dithering/color-mix you can get a bunch of colors.

And maybe the reason to why they choose those colors is because they mix better with this method to convert 4 colors into 45 different colors.

A lot old graphics looked differently on old displays.
Raw/unfiltred dithering usually looks really bad, but they can look quite impressive on the old monitors.

So, maybe the only way to figure out why they choose these colors would be if you could check how they looked on the intended displays.

Thanks king

Thanks you, king