Congrats and what a little beauty!!
I love the silver dapple coloring - both black and bay. There are other silver related colors as well - I'm not familiar with the Silver BROWN foal coat colors. Actually, don't think I'd seen/heard of anyone having one in the mini/shetlands. I'd been wondering if we had any, LOL... Know that that seems to be what is most happening in the QH/PH breed - the main stallion tested was a silver brown and he seemed to pass that particular color combo. The brown agouti is VERY similar to bay on the same allele, but different coloring action/look produced.
My silver black foals all have looked "gun metal grey" or "blue" w/ the light coloring around the eyes, above hooves, around the back of the legs & in the elbows/flanks. Our silver bay foals have had mostly white manes and tails and either high white stockings or completely white legs(tobiano pintos) so very little black markings to show the "silver affect" - making most folks think they are chestnut not silver bay. My smokey silver black colt looked PINK for months! Would have been perfect if he'd been a filly!
Will be interesting to see what your filly turns out to be. How fun!!