Is this 4 month old pup a bicolor or black and tan? - Page 5

Very Interesting....
It used to be that most GSDs were gray or silver with black, over time they went to cream, then tan, then red and now indeed some are nearly brown and black, and you can't get far in some show rings with black and tan color anymore, you need Black and Red.
 
The underside white that Kitkat must be speaking of is called

Pangaré - (Wikipedia)

in horses. This used to not matter in the GSD and most GSDs and VAs had the trait. But it has been bred out of most German Show lines. This trait is extremely common in wild mammals (horse/gazelle/lion/Leopard) and might have to do with camouflage or exposure to sunlight.
VA(JSV) Vego aus Wattenscheid

​
Some breed/s that almost always insists on this under white all the time now is the Akita Inu, the Shiba Inu and the Pembroke Welsh Corgi.

Also, feel free to talk about color and dogs using examples from the database that has over 1.7 million dogs now. Use older dogs if you wish from decades ago. It can be fun. I'm waiting to learn what the proper name for this under white is (In Canines). I think someone/s here has/have already started calling it the Hobo markings, or reverse mask. 
 

I thought we were only talking about head markings / colours
​when discussing facial reverse-mask or 'Hobo' markings ?  Don't
think anyone was trying to draw conclusions about body-colour
or 'white' underparts.  ;p
 

Pretty dog Starr!  Best of luck with her!   My boy jack says hello!

It looks to me more of a bi-color than black and tan. I have a West German GSD and she is black and tan, I also have an East German GSD male that is more bicolor.  You can tell the difference.  Yours looks to be more of East German heritage - nice looking dog!
 

Your pup would have to carry the solid black gene because her mother is a dark sable out of a sable to a black.  Sable/agouti is genetically dominant..  A black can only throw the black gene to its progeny.  The mother of your dog was also sable/agouti carrying black.  If she had thrown her sable gene to your dog, your dog would also have been sable since sable is dominant.  Since your dog is black and tan, the mother had to have given him her recessive black gene.

The gene for the two-tone pattern (black and red/tan) would have come from the father. 

(Bicolor is a term that actually means two colors and although it is often used for very dark dogs, there is much argument as to how dark a dog has to be to be considered a bicolor.  Also, genetic solid blacks can have so much of the lighter tan/red/cream/silver ground color showing that it may be impossible to tell such a black from a bicolor.) 

 

From pics pup seems have tan on ears and what I would call dirty feet but no true pencil marks so its a black and tan.To me the best looking Bi-colors out there have solid black heads or a tiny bit of tan for cheek specs,and only a tiny bit of tan on legs right before it reaches the paw with very black distinct pencil marks and very black rich full tar heels.Bi-colors at their best are extremely nice looking.

She is now 7 months. The tan around her face and neck has gotten a lot darker, belly is still black, she has light fur on the underside of her tail, groin area and under her armpit area, no ticking down her back at all, still has black on her hocks, but penciling on the toes has faded a lot. Thoughts?

I myself say she's about as close to what draws the line as could be....
lots of help there , huh! 
    She's a beauty none the less...

Thanks, Kitkat! I will be interested to hear what others have to say. She is just not lightening up as I thought she might. I personally love her coloring and don't care how it is defined, but just would like to get opinions and learn better how to distinguish between bicolor and black and tan/red. Two of her siblings are dark sable, one has coloring like her and the other is definitely a black and tan, albeit with a fairly dark mask.

She looks like she is morphing into a Bi-color> She is BEAUTIFUL!!!!  

My boy Rollie had a bit of tan on his checks & chest as a pup, then it disappeared and turned to black