Blue GSD health issues? Health

no he is blue and tan

There is always a certain amount of luck in getting a pup, but choosing one from a reputable breeder who does all the health tests and who preferably works the dogs in some kind of venue seriously stacks the good odds in your favour. Papers don't mean a good dog, but at least with papers you can check back the health testing for several generations, and if the pups come with no papers then that is a serious red flag. :?

Are you sure your pup isn't a blue sable? The sables often get a stripe of different colour down the back as their coat changes?

mother is a very light black and tan dad very dark with a little tan

Not entirely sure what you are asking - difficult for people to comment without seeing a decent photo

the pup was born blue and tan is it possible for him to get a coat like a sable gsd

The thing is that colourings of GSD are not necessarily clear for non GSD people.

For example my dog is a Grey, that is the colour they are called in Germany. In the UK they say Grey Sable,

When he was born, he was completely tan with a black mask and black v on his tail, he looked like a Malinois, he is now very dark.

I agree, hard to say without posting a picture. My dog is a fairly dark sable and some people think he didn't look that different from a black and tan at birth until you lift up the hairs. The dark hairs on a sable are light underneath.

However, I was under the impression that one of the parents have to be sable in order for pups to come out sable? So if they are black and tan then it's unlikely..

Are you sure it isn't just his adult coat coming through? They normally get a thicker/shinier/wavier strip of hair along the back and in patches when the adult coat starts coming through..

German Shepherd Colour genetics

Long while since I studied genetics and it always made me go like this...:? But if sable is dominant then you can only get a sable pup if one of the parents is a sable? (because they can't carry the gene recessively?) Is that right?