I'm not sure who to contact at Logos, but I 
need some guidance.  I'm finishing my doctoral dissertation and 
currently focusing on Colossians 2.16.  The Greek word for sabbath in 
this verse is σαββατων, which is plural.  There are 9 occurrences of 
that form in the New Testament and all of them translate the plural 
Greek noun with a singular English noun sabbath, the sabbath, the 
sabbath day, or the first day of the week.  
What I've found so 
far is that since the other coordinating nouns, festival and new moon, 
are singular, σαββατων is also translated as singular.  Douglas Moo in 
his commentary in the Pillar series states that σαββατων is regularly 
translated as singular reflecting the underlying Aramaic word  שׂבתא
But that really doesn't explain it very well to those of us less initiated in the nuance of Greek and Aramaic/Hebrew.
Any insight?
Jeff Trostle