Color genetics are so much fun but can also be sooo confusing.
The first mare is a silver of some type - w/o testing can be hard to determine which (silver black, silver brown, silver bay). I have two mares that I had tested - I swore they were silver bays - but they tested heterozygous black, heterozygous silvers.
The stallion with the white blaze appears to be a silver black. CONSIDER this - her foal could be a homozygous
silver. Our two mares that are homozygous silver "present" as palominos at differnt times of the year. I almost fell off my chair when you stated that she'd been born bay - but completely lost all the black in her coat in 6 weeks. That's a new one to me, LOL. Sure don't see any black in the 3 photos you posted.
Here are two photos of a mare that is homozygous (tested) silver, no bay and heterozygous black:
In May 2012, Bell at 20 years of age.
In March 2013, Bell, at not quite 21 yrs of age:
Since this mare is heterozygous black, she has produced several palomino & buckskin offspring when bred to palomino &/or cremello stallions. All of those foals carry a silver gene that can be passed on - some have been tested, some have produced silver when not bred to silvers or chestnut that are silver carriers.
Your 2nd foal looks to be silver based (to me). From the pics, I'm not seeing good leg color (some my silvers are impossible for me to see leg markings on except at birth or when they are clipped). Someone mentioned "goggles" - but the only lite hair I see is in the 2nd pic and I've seen that with my silver blacks (tested). The other pics don't display any goggles. In the bright sunlight, I've found that my silver foals seem to go thru a fade stage where they all look palomino in their foal coats... You can see the difference when they are clipped or when they shed out as yearlings.
Neither of these fillies carries a cream gene - both parents of both fillies have been tested. I haven't had them tested yet - this weeek it goes out. Both have a possibility of being homozygous silver, the closer/larger (Shamrock) one could be homozgyous tobiano. The smaller filly is Classy.
Here is a photo of Bell (1st two pics) in March 2012 w/ Classy just hours after her birth (Bell is not shed out yet) on 29 March 2012:
And yes, from year to year, our silver mares have different shades to their winter coats. You track it from 2009 to current on the two mares Bell and Bit from our website... The foals often have different shades in different years, too...
On your stallion - I don't know. Personally, I would say w/o testing that he's a combo of appaloosa and pinto markings - making him "extreme white". DW is a fairly new test and I don't know anything about it other than what I've read about it on the Animal Genetics website out of Florida... Since that one foal appears to be a black based silver - you might be able to say he is at least heterozygous black (Ee), but from there?