BLRW should be bred to BLRW to produce BLRW. It is recommended that you don't cross silvers to golds to BLRW as you will be set back years trying to get the correct color. There are articles that state an andulsian blue was bred to the Wyandotte to get the blue color.
Within BLRW, there is Splash, Blue and Black Variety. There is a chart showing the breeding combinations that is very helpful. Give your little guys some more time and you will see what you will get.
The black looks a bit different than other BLRW chick pics I've seen, but you will find out in a few weeks. Keep us posted and best of luck.
Where is everyone getting their chicks from? I'm buying from breeders directly and it's a bit more costly, but the quality is definitely better than the hatchery chicks.