Splash and Blue Splash are used interchangeably from what I've seen, though it does seem like most people who are actually working with these birds call them Splash.
They are not quite genetically the same, as Splash occurs with birds that carry two blue genes (b/b) and blue occurs in birds that carry just one blue gene (B/b). Blue is partially dominant, so if you breed a Blue bird to a Blue bird, you get 25% Black (B/B), 50% Blue (B/b), and 25% Splash (b/b) offspring. So they are related colors in a sense, but not genetically the same color.
As an interesting side note here, Blue and Black are both accepted colors of Ameraucana, but apparently Splash isn't, even though Splash is a natural outcome of Blue X Blue breedings. Oh, and there isn't a Lemon Ameraucana in the standard, nor have I heard of any lemon projects, but that doesn't mean they aren't out there somewhere.
(Hope I didn't bore y'all to death.
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