Can I breed a blue Silver Marten to a Black Silver Marten. Will it mess up coat colors or eye colors?
That should be a fine cross. Blue is dilute black, so you'll get all blacks in the first generation unless the black parent also carries a dilute <d>, in which case you'll get both blacks and blues. Either way, all the babies will carry a dilute allele, so paired with another blue (or dilute carrier) they'll make blacks and blues.
It should not mess up coat or eye color at all. The only time breeding a black with a blue would be a problem is if the black and/or the blue weren't really
black or blue, e.g. they were actually a self chin or a self squirrel, but that's not genetically possible in silver martens.
In my Satins, I find that for some reason my blacks start to get thinner coats after several generations of breeding black to black. But my blues are always dense, so I cross blues into my blacks frequently, to keep the coat density where I want it.