I think people are getting confused here's what it sounds like to me happened:
The mare was exposed to a stud colt by accident a while ago (the paint) the foal was still-born. Since then she has developed an injury that makes her unsuitable for riding or showing, so the owner decided to breed her to the palomino stallion. Considering the fact the mare came back in heat the first time she came back from the stud it sounds like the colt didn't breed her again either. So she's definitely pregnant from the palomino stud. It was irresponsible to breed without checking for frame - but it was a mistake, it was made, we can't all be perfect. I hope the foal comes out healthy - either way it sounds like Silver has learned the importance of checking in the future.
As for color possibilities:
If the stud carries agouti:
Black, Bay, Brown, Buckskin, Brownskin, Smoky Black
Black or smoky black
As for the pattern, depends on the mare could be any or all of her patterns.
Good luck with your foal :) I hope all goes well! Pictures are a big Must!