This is not my horse. He is kept in the same pasture as my colt though.
I've known this horse since he was born, and have been tracking this marking since then.
These pictures were taken today - camera's date is off -, and this is him pictured with my own colt, Midas.
As you can see, he clearly appears to be a bay tobiano with splash and sabino, just like my colt Midas, who is seen next to him. The colt in question is on the left, and the marking that is odd is that roan-y area on his cheek. It almost appears as if he is greying out.
Now, when he was born in the place of that marking were two GOLD colored smudges. By gold I mean palomino-gold. The nearly solid white part of that marking is where the first gold smudge was. The marking area then over time turned silvery, then the white-grey, and has spread. The colt is now nearing a year old.
The colt's dam is a Seal Brown Tobiano (with sabino.). More confusion comes in about his sire. The mare was bred -on the same cycle- by two different stallions. (again, not my mare, I had no say on her being bred or anything of the like. XD)
Stallion 1 bred her first, he was a black based grey arabian. Stallion 2 bred her at the end of her heat cycle and was a bay tobiano.
If I do so recall, a brown horse cannot produce a bay unless bred to a bay, correct? He doesn't really seem /grey/ either to me though. Which leads me to believe his sire was the bay. That still leaves the question about his marking though, could it be a mutation of some sort? I just haven't a clue what might be doing it and am extremely curious to hear other people's thoughts on the strange marking.