My understanding is that eye shine color has a relationship to genetic coat type...i.e., silk (blue, green, gold) vs cotton (red)...not genetic coloring (MM=Black...Black being the recessive color condition and lacking 'greying' genetics). It is also my understanding that Yorkies who break blue 'later' may stay at maturity a more 'desirable' color...i.e., closer to the standard "dark steel blue" color...than those who break blue earlier. I personally think all the colors are gorgeous, though...
...and I just marvel at the variety...they are all just such cutie pies!
Oh, and my Mia is "golden" but her skin has a blue cast even though she lost all the black hair of her puppyhood.
The YTCA (and AKC) say their color does not fully mature for 3 or more years, though, so I wouldn't worry about your lovely girl. Unless my eye adjustment was a complete failure
, there appears to be blue on her head so it looks like she may not be black and tan forever...IMHO.
Your Yorkies are so precious, and what a nice photo that is of them all together...love the matching bandanas!