good info so far!
yes all cinnamon babies have plum coloured eyes, but not split cinnamons.
greywing is recessive, so a chick must receive a greywing gene from each parent to be greywing. the parents do not need to be visibly greywing, they could both be split for it.
one greywing gene and one clearwing gene gives full bodied greywings.
if you mix cinnamon with greywing it gets tricky to tell if they are one or the other or both! always pays to make a note of chicks with plum eyes to help with future id.