Your chances would pretty much be 50/50 for a grulla or a red dun, with bay dun also being a possibility if your mare carries agouti. However, the dun is by no means guaranteed - you're almost just as likely to get another sorrel foal depending on the zygosity of the genetics on the pair.
I would love a sabino Arabian - I think they are gorgeous. I've planned for awhile to breed my mare to Khartoon Khlassic. Am I doing it because he's sabino? No. I'm doing it because I love the way he is built. The sabino is a bonus, even though I'm aware she may not throw a sabino foal. If Khartoon Khlassic died, would I breed to his accomplished son Pikhasso? Probably not - I am not fond of the way he's built even though he has sabino.
We all have colors we'd love to have, but buying is the only way to get those colors in a good looking foal. We all love unique colors, but breeding is a crapshoot at best. My chestnut mare comes from many lines of bays and blacks, her dam was bay and her sire was black and oh, lookie, another dang chestnut! That's the way it is though - you simply cannot breed for color. If you manage to find a good stud with a color you like, it's an ok risk, but never a guarantee. But how good is the fun colored baby going to be when it doesn't have the conformation to do anything but sit in a pasture?