Colossians 2:16
16Therefore let no one pass judgment on you in questions of food and drink, or with regard to a festival or a new moon or a Sabbath.
The short answer is that this is referring to the ceremonial law (and possibly the civil law given Israel) that went with certain sabbaths or even every sabbath under that, which does not apply to believers today in light of Christ's fulfillment of ceremonial law (and the ending of the Old Testament theocracy of Israel).
See Numbers 13 for examples of ceremonies, feasts and sacrifices that were required then on certain sabbath or every sabbath.
Remember, the moral law, summarized in the Ten Commandments is binding on all men in all generations, including the fourth commandment.
It is not eliminating the fourth commandment (work six, rest one).
So while the Christian sabbath (Lord's Day) does not have the ceremonies and sacrifices that prefigured Christ, it is still characterized by the same principles of the fourth commandment:
1) advance preparation
2) abstain from work
3) abstain from recreation
So that the day is made "holy" (set apart) from the ordinary aspects of the rest of the week by "sabbath" (resting) from them.
This, in order to prioritize the worship of God, corporate, family and individual, all the day.
You may find the first part of this recent thread helpful:
http://www.puritanboard.com/f17/objections-sabbath-using-colossians-2-16-a-71565/