You may or may not know, the Doberman breed comes in four "acceptable" colors: black and rust, red and rust, blue and rust, and fawn and rust. The Doberman Pinscher Club of America has a page, and chart, on Color Inheritance, if you're interested. I remember drawing those squares back in seventh grade science class! In short, though, Black is the dominant color. Red is the other primary color (for lack of a better word. Black is dominant over red, however). Blue is a dilution of the Black Dobermans, and Fawn is a dilution of the Red (sometimes referred to as "brown", depending on who you talk to).
Cinnamon, the Doberman pictured above (and you can read the story about this picture at Snopes.com) is red and rust. From my message board reading, once you deviate from the standard black and rust, people start having a hard time identifying a dog as a Doberman. A top guess, for the reds? Vizsla.
You'll remember Blue, who is blue and rust, from my post regarding her loss in South Carolina. To my knowledge, nobody has seen Blue or come forth about her since. Hopefully, she's living happily with a family who is treating her well.
Whisper (remember Whisper?) is a blue girl as well.
Olivia is a fawn Doberman, one of the Doberman Assistance Network's recent cases. The picture is linked right from their site, and is not mine.
It is frequently, though not always, the case with blue and fawn Dobermans that they have a problem with their coats, called Color Dilution Alopeciam, which may result in things like a thinner coat, a brittle and dull coat, and even baldness. A good diet and supplements of things like sardines and fish oil can really help with this, I hear (Doberman Talk is a wonderful place, have I mentioned that? Many owners, some breeders, and in general people who have been in the Doberman world for decades congregate there, swap stories and advice, and in general have a good Dobertime).
And the last Doberman color, the one that may not compete in AKC conformation events, is the Albino Doberman. Pierce, below, is also linked from the Doberman Assistance Network case page.
If a Doberman is an albino, he or she has "WZ" in the AKC registration number. Dogs who have an albino in their direct line, regardless of presented color, also have "WZ" in their registration number. There are varying stories on Albino Dobermans; people who breed them on purpose say that they are not displaying true albinism, sometimes refer to them as "cream" or "blonde", and will frequently jack up the price for their puppies.
People who feel that the deliberate breeding of albino Dobermans is not ethical highlight the health issues (visual light sensitivity, skin prone to sun sensitivity, skin lesions) and potential behavioral problems that albinos display. From the Doberman Pinscher Club of America web site: "Poor temperament is a significant concern. Due to the intense inbreeding to obtain the mutation, the temperaments on a great many are totally unstable. These problems range from fear biting to outright vicious attacks. Shyness is prevalent. " What does color have to do with temperament? On its own, perhaps nothing (though you'll hear varying amusing stories about "red boys" versus "black girls" and things of that nature.) However, there does seem to be a genetic component to temperament. Since breeders who deliberately select for albinos are not considered ethical breeders, they also tend not to have Dobermans who are proven in any venue (conformation, sport, or working) and may not in fact be "suitable" for breeding. Bad breeding leads to bad temperaments, unfortunately, and it's the dogs that suffer while the breeders pocket the cash and start again (what, you think shy dogs like being like that all the time? Think of how anxiety can wreck humans).
Not every Albino Doberman has all of these problems; indeed, there was a shakeup last year when a rescue albino Doberman, Sprite, was invited to the Doberman Pinscher Club of America Obedience Top 20. The DPCA does not support the breeding of albinos. The AKC registers them, with the concession of the "Z list" and the fact that an "unacceptable color" is an automatic disqualification from the conformation ring.
While I do not support the breeding of albino Dobermans, they are occasionally in rescue, and do still need homes. They are still Dobermans. I would rescue or adopt one, I think, were I sure that the dog was temperamentally stable (as sure as one could be, anyway!) This can really be a hot button issue amongst Doberman people, and I don't want to raise any hackles, but you can't talk about color without talking about albinos as well.
The flip side of this is Dobermans who are melanistic: all black, with no (or very very faint) rust markings. It's hard to find pictures of them, and the one that I did find also has her pedigree posted, I guess to prove that she's purebred. She also has a WZ registration number.
It is also worth noting that not any one color is more "rare" than another (other than albino) and you should certainly never pay a premium price for a "rare blue" Doberman. A breeder can make reasonable guesses regarding what colors will be in a litter, and indeed, many reputable breeders in fact know the color phenotype of their dogs. Black Dobermans will, I think, always be my favorite. I do have a fondness for reds as well, though, so who knows, maybe sometime in the future that will be what I go with?