appaloosa coloring

i just had a new foal born and i'm trying to figure out why he is entirely white.

none of his white markings (splash, overo, sabino, leopard, and rabicano) should make him entirely white, and i was very hopeful that he'd only have visible leopard spots along his topline (like most homozygous splash leopards do), with some obscured by his overo markings. 

i'm assuming it has something to do with the wonky way white patterns interact in appaloosas on EV? I'm not super familiar with the breed, but i know i've had splash and overo do weird things in the past.
any insight? thanks in advance!

It's the overo + Sb. I played around with the custom horse creator, and everything was appy until I added the overo and Sb together. Without the overo (but w/ Sb) you get appy and without the Sb (but w/ the Oo) you also get appy, but together you get sadness. ;)

alas! that sneaky sabino and overo! 
well, at least the spots on white looks pretty cool.

thanks for doing the experimenting to find out the cause, i didn’t even think of that!  :)