I have one frizzle right now that some days looks blue and some days looks black! 
I think the darker ones come from black x blue breeding, lighter ones from blue x splash, and nice even ones from blue x blue. Even splash has varying degrees of blue thrown in. Fun fun!
I think you'll have to wait till they fill out a little more to be sure, but with mine, of they hatch yellowish, they stay splash. If they are going to be blue, it's obvious blue at hatch. Even a few light feathers to me makes them splash. Jmho

I think the darker ones come from black x blue breeding, lighter ones from blue x splash, and nice even ones from blue x blue. Even splash has varying degrees of blue thrown in. Fun fun!
I think you'll have to wait till they fill out a little more to be sure, but with mine, of they hatch yellowish, they stay splash. If they are going to be blue, it's obvious blue at hatch. Even a few light feathers to me makes them splash. Jmho