It's really hard to tell from just the one picture. Is there any way you could get some more detailed pictures, especially clear ones of her legs and her butt/back from directly behind her so that the dorsal stripe is clearly visible?
Just going from the single picture, though? I would say that she's a brownskin/smokey brown. It's very similar to buckskin, just with a different version of the Agouti (the gene that restricts black points and dilutes the body...causes bay and brown. Bay is "A" and brown is "At"...I think). Typically, brownskins are a lot darker with supercharged dapples as compared to regular buckskins.
Also, unless the sire was a palomino dun, I'm almost positive dun does not exist in Belgians - in fact, I do believe they're almost solely "base" colors - black and chestnut with potential for modifiers such as agouti and grey only. I would agree with sooty brownskin/buckskin. Posted via Mobile Device