I've collected dyes for a long time, and used few of them, so I've got large stacks of all kinds of dye (except black. sold that.

Now I want to get into dyeing and want to test dye mixes. Now my question:
What happens if you apply a stack of X vials of dye A to a stack of Y vials of dye B?
(X and Y being numbers, especially if x != y)
Will this consume the whole stack A and B and turn it into a stack of mixed dye, or will it take 1 vial of A and 1 vial of B and turn it into 1 vial of mixed dye?
I don't wanna waste two large stacks of dye for a test, so I'd really like to know the result beforehand, you know.

Oh, and while we're at it: Has anybody found a way to unstack dye stacks without the help of an other player?