I just emailed our club secretary about these blue genetics. He is our go to guy for genetics.
"With simple blue in ducks it works the same way as blue in chickens. The blue dilution is incompletely dominant. If you breed blue to blue you will get 25% black (no dilution), 50% blue (one 'dose' of dilution) and 25% silver (two dose). Yes, in ducks it is referred to as silver but in chickens it is generally referred to as splash.
Lavender is kind of a confusing term because people are using it to refer to different things. The Silkie people are calling their new variety of Silkies lavender but it is actually self-blue (which is a recessive trait without lacing on the feathers). Lavender in ducks is different with alot of people. Most refer lavender if the have the blue gene AND the chocolate gene. In Muscovies you have lavender and lilac varieties. Lavender can be confusing but if you are working with simple blue genetics the term is silver. "
Hope this helps!