Brown tails and darker/overlaid black tails are actually pretty common, yours has a lot of black speckling so it would make sense the tail was darker.
Rich covered it as far as albino goes, it's a recessive trait which means the snake will look normal but carry the 'hidden gene'.
The only possible marker I have ever heard of is the 'light bulb' eye, where the top of the eye is much much lighter than the skin's base color around it, it's most noticable when young and when compared to siblings. Jeff Ronne posted about this some years ago on the KS forum.
Here, I found a post from Jeff in 2001 on another site that discusses this:
http://www.redtailboas.com/forum/bre...t-litters.html
However, I've produced 100% hets that don't have this 'lightbulb' look and seen some non-hets that would appear to have it, so I would not personally consider it a verified marker. With boa hets, you just have to trust the source where you are getting it from
Good luck!
-April