I have already posted this once and forgive me for doing it again but I am getting a couple of private emails again on this. You can cross lavender with any color you want but there are certainly some that will make the challenge easier and some which will make it harder by making some colors just muddy, like splash. Remember that self blue/lavender and blue are two different families. This is a quote from Donnie who "leads" me in the right direction on this lavender breeding.
Yes they are in entirely different families. The blue gene is a incomplete dominate gene, and the Lavender is a recessive gene. When the two are crossed together, the lavender will dissapear the first generation because each individual will carry only one copy of the lavender gene (mutt). The colors that will show up will be the same as crossing a black with the blue or splash. When the blue is crossed with a black the result will be 50% blue and 50% black. When the splash is crossed with black you will get 100% blues. You now have blues and blacks and they all carry the lavender gene but none of them express it. When this generation is mated together, you have a good chance of getting lavender, black, blue, splash. The black, blue, and splash may or may not carry the lavender gene. You can't tell which carry what, and another thing they all can look very similar at hatching, you can guess which genes they carry, but that's about it, you're bound to be wrong a certain % of the time.
You see what kind of mess comes from this? The genes get inter mingled and it is impossible to predict what each mating will produce. Why get into a mess like this, just don't cross them.