Just thought I'd throw this up. It's the meat of the article, and why Harls shouldn't be bred unless you think that bringing deaf deaf puppies into the world is something you want to do.
HARLEQUIN to HARLEQUIN: You can expect, in a litter of 7, to see 2 (likely mismarked) black or Mantle pups, 1-2 merle pups, 2-3 harlequin pups & one deaf white pup (two are statitically conceived, but one of two whites conceived generally dies prior to birth). Naturally people have 7 males in some litters, so some people will have 7 harls..or even 7 deaf whites, but on average, about 1/4 of the four basic colors is what is expected. Of course harls that carry blue or fawn or brindle can produce these "porcelain" dogs, sometimes called bluekin, fawnikin & brindlikin respectively. To read about why fawnikins occur, click here. Flashy harls (with lots of white) could also produce piebalds: white dogs with "mantle heads & harlequin looking bodies" as they have been described. Harl-, merle- or boston-heads; dogs with white bodies & "caps" of color (i.e. color-headed dogs) also can result from the use of piebalds & flashy harls & mantles. These color-headed dogs, also called piebalds, are essentially mismarked Mantles. To read more on piebalds, click here. Any time two dogs with the merle gene (incl. harls) are bred to each other, white merle (i.e. defective, dominant white) offspring are to be expected. The dominant whites that do survive to birth are normally defective & commonly deaf. Ethical breeders have traditionally euthanized most all whites at birth for these reasons. To read more about white (MM) danes, click here.
HARLEQUIN to MANTLE: This is the preferred breeding, all things considered, as it does not produce the Dominant (deaf ) White dane. Expect the litter to be about 1/2 mantle, 1/4 merle & 1/4 harl. So in a litter of 8, expect 2-3 harls, 1-2 merles & 4 mantles. If these black pigmented dogs carry for other pigments, you may get fawns with blazes, or blue instead of a black basecoat. (If that is confusing, read about why fawnikins are here to stay.) Piebald & color-headed dogs can occur, especially when flashy dogs are used.
MANTE TO MANTLE: Produces only Mantle: that is, it cannot produce harl, merle or white danes. Now piebald danes that are mistaken for whites and for harlequins can be born to Mantle parents. This is more likely to happen when breeding flashy Mantles with big collars & broken blankets than with dogs who have more pigment. Mismarked blacks can also be born to this breeding as can piebalds, so this breeding doesn't promise all show marks, it just guarantees having nothing but black and white dogs. It is possible (if unlikely!) that very flashy Mantles bred to each other could produce a puppy so white s/he could be deaf. Possible--not probable--& AFAIK it's never happened in Danes. BUT it does happen in Boxers & Dalmatians.
MANTLE TO (harl-bred)BLACK. Would likely produce mismarked blacks. Mantles & (solid) Blacks also are possible.
BLACK to BLACK: Would likely produce mismarked blacks when harl-bred blacks are used. Mantles & Blacks possible.
BLACK TO HARLEQUIN: Produces as does Mantle to Harlequin, except, since a Black lacks the white collar of the Mantle, expect more mismarks under the AKC standard to occur, both in Harlequin & especially in potential Mantle offspring. Blacks will likely not be solid Black, but mismarked black, sometimes even called "harlequin black" it is so common to black to harl breedings. These "harlequin blacks" are disqualifying under the American standard.
Taken from http://www.chromadane.com/harl2merle.htm