I beleive Paul was teaching tolerance of those involved in “religious holy days” like New Moon celebrations.
Just as today we should be tolerant of those who observe Good Friday and Easter as “religious holy days”.
In Colossians it's more than likely that there were some that were attempting to tell early Christians HOW to observe the holy days of the Lord. All sorts of Jewish traditions had been built up over the holy days and some were elevating these traditions.
Reading Colossians 2 makes it clear that a number of man made, man based ideas philosophies and traditions were being elevated and forced on those who were observing the Lord's holy days.
The art and act of the sighting of the new moon and the testing of the barley are deeply scriptural, and absolutely necessary for the maintenance of a scripturally accurate calendar.
Good friday is the worship of Fish god Dagon, and easter the worship of ishtar. Paul would in no way allow respect for such abominations.