"Splash" in chickens results from them having two copies of the incompletely-dominant Andalusian Blue gene. "Blue" results from having one. The gene dilutes black in both cases, and can dilute gold when there are two copies (I think...don't remember for sure).
"Lavender" (some breeds use the term "Self-Blue" but it's the same gene) is an autosomal recessive gene, meaning the only birds that show the trait must have two copies of the gene. It acts as a diluter of black (and gold, I think...not sure because it doesn't matter to me so I didn't learn it. I like the idea of a flock of black and "shades of gray" birds.).
What happens in Blue birds is that the black is not evenly diluted -- typically there is lacing on feathers (less dilution at edges, more in centers), and males are darker in the neck, back, hackles and tail, with lighter breast). Lavender birds are more evenly diluted. So in these Blue-Lavender birds, you see the basic Blue dilution pattern in the roo (darker neck, back, hackles and tail, with lighter breast) but the each part is diluted down a notch further. To me, it looks like a lighter blue roo with a lavender breast. The hens (to my eyes) look like a lavender base with faintly-darker hints of lacing.
I realize that this means they don't fit the SOP's descriptions of either Lavender or Blue, but I don't care. This was just to satisfy my own curiosity, and now it's a little mental note I'm filing for when I can have my own flock of utilitarian fowl, all in shades of black and gray (Marans, Jersey Giants and Ameraucanas in chickens, plus guineafowl and Muscovies...and maybe even Slate turkeys!).
ETA -- Are you saying your bird is a Splash, or a Blue? I'm confused.
It does resemble the birds in the pics I posted, but I've never seen a Splash roo keeping the even pattern of dark feathers on top. I have seen pics posted on other threads of very light blues that don't have the Lavender gene that also look a lot like the birds above. Also, are you sure your bird doesn't have Lavender? The tail feathers seem to show some of the "narrow" trait that is associated with Lavender, but that could also be something unrelated. I don't mean anything bad -- I'm just trying to figure it all out. I've seen the B/B/S in the three breeds I mentioned before this edit, and I like the variations. I've also seen the Lavender Ameraucanas (technically project birds), and also liked them. So I was wondering what would happen if I didn't bother separating the Ameraucanas into one B/B/S group, and one Lavender/Black group. I know that in Muscovies, there are birds that are genetically Blue-Lavender or Silver-Lavender (Silver is equivalent genetically to Splash in chickens), but I didn't get to see what they looked like until recently.
I know, with all the beautiful patterns out there, here I am drooling over shades of gray. I never claimed to be normal.
