First, I completely agree with all the posters on here.
However, I will go into your color question, as I'm obsessed with horse color genetics. NOT with getting certain colors out of my breedings, but knowing exactly what horses are and what possibilities there are, just because it fascinates me. I've even had a GELDING color tested due to my obsession ;)
Anyhow, it may not be possible, AT ALL, for your bay dun to produce a palomino or a grulla. If she is EE, you will NEVER get a palomino. If she is AA, you will NEVER get a grulla. If she is both EE and AA you will NEVER get either, no matter what color you breed her to. The only way to know is to have her tested. You can get extension and agouti done for $40 via Animal Genetics in Florida.
Palomino is ee and nCr. Doesn't matter the agouti status.
Grullo is E_ aa with the dun gene.
I'm tempted to get Denny done just for curiosity sake; I'm pretty sure he's a Sabino chestnut, but someone said he was probably Smoky as well; he has dark spots and darker chestnut points, and his tail is really dark compared to his body. Hm.