I would like to underscore the comments of Karlis Karklins concerning
     color identification (whether in bottles, beads, or anything else).
     Although the Munsell system is good for standardizing description
     (anyone else can look at the same color chip in their own book and
     know exactly what you observed on your sherd), we should acknowledge
     that manufacturing methods in the past were not conducive to precise
     quality controls for glass color, nor did consumers seem to care all
     that much.  There might be a great deal of subtle color variation in
     one vessel--and certainly among a batch of vessels made at the same
     shop.  But to most of us--then and now--green is green, and blue is
     blue.  Splitting beyond that level may well be drawing a distinction
     without a difference.
 
     It is not necessary to hit the bullseye to be effective with a hand
     grenade.  As long as you come near the target, it should prove quite
     effective.  As Karlis points out, employing a range of Munsell values
     makes far greater sense theoretically, and it makes the analytical
     process much less maddening in practice.