Today I noticed one of my young Buff Orpington pullets has a definite splash pattern. She's solid buff, but has several darker buff feathers dotted all over her plumage
Cara, I've seen that on buff plumage when they're moulting/growing in new plumage. Mark the hen and check her again in a few weeks to see if it goes away and becomes more evenly distributed.
Well, that looks more like a mottling gene lurking. Certainly not unheard of, especially in blacks. They hide all sorts of colors sometimes. And it would make sense on your multi-colored buff as well.