I am thinking that she is a silver buckskin as well. The reason is that most often the silver takes a few days after birth before it starts to show in the in the mane and tail. Remember, that one of the dead giveaways on the silver gene is that the roots are dark on the mane and tail. So this would account for the dark mane that has gotten lighter.
Now, we know that the mare is a cream carrier since she is a palomino... But could she actually not be a palomino but a light sorrel with the silver gene making one think she is a palomino? Could your mare really be a silver buckskin? She would have to carry silver if the foal is a silver buckskin. What color are her parents and grandparents? That may help you to decide that. Also, she would have to carrie Augoti (bay gene) as well because the sire is black assuming that the foal is buckskin. So with this info, the foal would have a 50% chance of inheriting cream from the mare, 50% chance of silver, 50% chance of Augoti assuming that your foal is a silver buckskin.
The sire on the other hand is black and he is NOT homozygous for black since he has a full sibling that is palomino. The sire also does not carry silver or augoti as that ALWAYS shows on the black coat. On the other hand, the sire has a 50% chance of being a smokey black as one of his parents has at least one cream gene. The question is was one of those parents a double dilute? If so, then you can guarantee the smokey black. Also, has the sire EVER had a buckskin or palomino out of a non-dilute mare? Or has he ever sired a cremello or perlino (double dilute)? If the answer to this is yes, then you are guaranteed that he is a cream carrier. If it were me, I would get this guy tested to know for sure.
Ok now, lets take a look at the cross between the sire and dam of your filly.
Your filly has a 50/50 chance of being either red or black in the base color. Since your filly has faded dark points, and the mane and tail showed black at birth, then I would say she is black in the base color. Now with the body being that redish yellow color, I would be somewhat inclined to believe that he has inherited Augoti... Does she have any bays in her recent background? But wait.... one other possibility exists! What if the mare was a silver carrier and this foal was black in base color and inherited the silver gene and the cream gene???? This is also a VERY real possibility. This would give you a smokey chocolate silver dapple? Not sure of the real name, but it would be a chocolate silver dapple with the cream gene. Anyway, this could easily give you the darker chocolate points and a lighter mane and tail as they mature.
And if we assumed that the sire carried cream as well as the dam, then the actual chances of cream being passed on to your filly is as follows:
25% of double dilute
50% of single dilute
25% of no dilution gene
In other words, if both parents are single dilute cream carriers, you actual chance of a cream carrier is 75%.
So if I were you, here is what I would do. I would test the sire for cream, and I would test the mare for cream and augoti. These tests are done with a mane sample and would answer a ton of your questions. If the dam's results come back as her carrying the cream and the augoti, then you know for sure that a buckskin is possible out of this cross. Now on the other hand, if your mare isn't an augoti carrier, then you can rule out a buckskin. And if you know for sure about the sire being a cream carrier, then you know that you can get a double dilute if you breed him to a cream carrier.
Of course you could just have the foal tested. That would tell you genetically if she was an augoti carrier and a cream carrier which I would bet she does carry at least cream. But this wouldn't tell you for sure which parent was the cream carrier.
Unfortunately, the foal can not be tested for silver, so one would have to decide once they know for sure what else the foal is. Testing would also verify the presence of black.
Hope I didn't confuse you any, but from the sounds and looks of it, I would bet she is a silver buckskin, and a pretty one at that.
