Here is a color calculator you can use to make some hypothetical crossings.
Playing around with the calculator is a pretty easy way to learn about some of the genes out there, but as @Cochins Elite stated, there could be unseen recessive genes at play. If your birds were aquired from a reputable breeder who kept their varieties separate and pure, then you probably won't have to worry about much. If they were hatched from a hodge-podge barnyard flock of many varieties all run together, then you may be playing a genetic lottery.
To answer your question there's no sure answer to your question. You would have to know your chickens family tree's.
Genetics is a very complex subject your chicks could take on recessive genes from its grandparents or great grandparents and so on.
It is only after several generations of breading the exact same colors that you will start to not see those recessive genes come out very often, but it can still happen.
you could hatch several eggs and have them all look different.
The only way you will have a better idea of what your chickens could produce is to give it a try and see how many chicks look the same. Only then will you start to have a idea of how stable the genetics are and what they could produce.
that being sed I am interested to know the results of experiment.
Well I guess I'm just gonna have to play around and experiment.
The buff and barred are from Wilco so, hatchery, mostly just for eggs, but it will be fun to see what they could make :)
The mille and the mottled are from a breeder. She says she breeds them together and gets mille and mottled, but I'm quite unsure.
I'm just gonna get them and see what happens, if the babies are just an odd mix I'll probably just use the mottled for another mottled hen and get the mille a new boyfriend lol
Thanks guy :)