After doing some more research and also consulting my supplier regarding the coloration of this particular C. cf striatus and researching Kuiter's book on Tangs, here's our verdict.
There are many different subspecies of C. striatus that simply get imported as C. cf striatus. Most cf. will go through a color morph after 2" or so, turning drabbish brown, unlike these Purple Striated Tangs which are well past that size.
Blue Line Tang is an Acanthurus nigroris, not a bristletooth; exhibiting a round body shape, found in Central Pacific. Purple Striated Tangs are isolated to Maldives and Red Sea.
Out of the 50 or so imported into the US, all juveniles under 2" showed drab colors while the adults 3" - 4" showed consistent coloration exhibited in my picture.
Here's another example of C. cf striatus that some of you might be referring to, often times coming from Fiji.
Juvi under 1.5"
http://www.qualitymarine.com/Produc...us-cf-striatus/Bristletooth-Orange-Stripe-Juv.
Adult over 4"
http://www.qualitymarine.com/Produc...haetus-cf-striatus/Bristletooth-Orange-Stripe
You can clearly see the difference in the pectoral fins, the tail, facial markings, etc. The subspecies in our care are well over the juvenile size that are known to trigger color change in other subspecies of striatus, but still shows retention of patterns / coloration, if not improving.
The validation that these will hold their colors comes from a supplier I've dealt with for almost a decade and also a respected individual in the industry that's well versed in unusual marine species, who also saw many different morphs of these fish imported over the years.
I guess like all things posted online, you can choose to believe what you will but we 100% believe his knowledge / information. It also looks like a few made it over to LiveAquaria and they seem to agree that it's completely different from the other C. cf striatus they've seen in the past.
Anyway, hope that clears up any confusion.
