Black, Blue, Silver (Splash), Chocolate (Dun) can all be interbred. It just depends on what you want to hatch. I would probably find a black drake and cross it with your chocolate hens, blacks tend to be more "refined" and will give you the higher Runner type you should add to your breeding pens. I've seen some spectacular blues as well, but it all depends on what you can find. We have a trout Runner hen, but no grey or trout drake for her, she's mainly to enjoy at our place. Chocolates are available out there. There were two at the swap meet a couple of months ago with decent type. I wish I had known.
Hope it helps you.
PS: Ask your mom about leg color in the cayugas...I mentioned it to her, but I don't know if she remembered to tell you. It can really mess up the breeding pens, but it can be fixed easily too.