If a horse is homozygous for certain genes you can increase the odds, but no, you can't guarantee like that. The stud being advertised is likely heterozygous for black and homozygous agouti- so he will never be able to produce a black foal (agouti will always turn it to a bay) but could produce a chestnut foal (on which agouti has no effect).
Since he's perlino, he's definitely going to pass along a cream gene, so the bay becomes a buckskin and the chestnut becomes a palomino.
What they're not taking to account is that the mare could also contribute a cream gene, which would produce a perlino or cremello. There are a number of other genes that could come from the mare that would affect the color- champagne, dun, pearl, silver, etc.
So for your average bay, black, or chestnut mare who's not hiding any other genes, you would be guaranteed a buckskin or palomino. But, breed any other color mare and the guarantee is out the window