It actually gets kinda complicated if your drake is Lilac since Chocolate is a sex linked gene (and my brain is not working very well right now)
Basically, a hen could only have one copy of the chocolate gene, and if she does, she is visibly chocolate. However, a drake can carry two copies. If he only has one copy of the gene, then he would not show chocolate. If we don't look at blue at all, then he would be black. If he is also carrying blue, then he would look blue even though he is has one chocolate gene.
So a Lilac is a silver with chocolate, but a drake would have to have two copies, so to get a Lilac drake he would have to have two copies of blue AND two copies of chocolate. However, you could get a Lilac hen with one copy of chocolate and two copies of blue.
So if you do have a Lilac drake, he would give one copy of chocolate and one copy of blue to *all* his babies. The hen, black, would give them no colors at all. So any drakes that result from that cross, they would not show the chocolate gene, but will show the blue, so they would be Blue.
The hens that result from that cross would show both the blue and the chocolate, and would thus be Lavender.
So what I said before was wrong. My brain was all muddled since it gets complicated with sex-linked genes.