Colossians 2:16 Therefore, let no one judge you in matters of food and drink or with respect to a festival, a New Moon, or Sabbath days.Paul was absolutely NOT saying that Christians are free to ignore God's instructions concerning eating, drinking, and His appointed times. He clearly stated just a couple of sentences earlier that he was talking about man-made traditions that men had added to God's commandments and not the commandments themselves.
Colossians 2:8 See to it that no one enslaves you through philosophy and empty deceit according to human tradition, according to the basic principles of the world, and not according to the Messiah.His point was that we don't need to expend a lot of energy worrying about whether we're doing it all exactly right. We're not priests entering the Holy of Holies. We aren't going to be struck dead if we eat something God told us not to or if we don't understand exactly what God meant by "labor" on the Sabbath. Only God gets to set the rules--not theologians--and He is eager to forgive our mistakes.
Don't worry if you aren't tying your tzitziyot exactly the way some rabbi says you should or about whether or not tuna is kosher. (It is. ;-) ) Focus on obeying God's commandments, not man's, and on walking as Yeshua walked. It's not complicated.