In great Danes, fawn is masked sable (AyAy EmEm hh mm) and fawnequin is masked sable merle with the harlequin modifier (AyAy EmEm Hh Mm). As such, the pair would breed true for the sable and mask genes (and thus fawn). The real variation is in the genes that act in that fawn. Probability-wise, half of the puppies will end up being merle, and the other half will be non-merle. Of the merles, half will be fawn merle (and thus lack the harlequin gene) and the other half will be fawnequin (and thus have the harlequin gene), All of the non-merles will be fawn since harlequin only acts in dogs that also have the merle gene
You would not get black or brindle from the breeding since both colors are dominant to fawn, but depending on what the parents carry, you could potentially get fawn mantle or blue fawn (fawn with blue pigement and a blue mask). There's also the other, more unusual colors that sometimes pop up in the breed, such as liver pigmentation and piebald.