The religion of Colossae at the time was the Hellenistic worship of Zeus, Aphrodite, etc. However, the Colossians were also into astrology and maintained an openness to non-pagan religions, including Judaism. Paul had learned that this mentality had infiltrated the young Christian church there and charges them:
So, as you received Christ Jesus the Lord, walk in him, rooted in him and built upon him and established in the faith as you were taught, abounding in thanksgiving. See to it that no one captivate you with an empty, seductive philosophy according to human tradition, according to the elemental powers of the world and not according to Christ (Col. 2: 6-8).
Let no one, then, pass judgment on you in matters of food and drink or with regard to a festival or new moon or sabbath (vs. 16).
If you died with Christ to the elemental powers of the world, why do you submit to regulations as if you were still living in the world? “Do not handle! Do not taste! Do not touch!” These are all things destined to perish with use; they accord with human precepts and teachings (vs. 20-22).
Syncretism reflects the blending of ritualistic elements of unrelated faiths. It is distinct from religious pluralism, which affirms that different religions offer alternate paths to salvation, disregarding their disparate claims to the truth.
The following is from Pope Francis’ Querida Amazonia. Compare the language here to the language of St. Paul’s scolding of the Colossians. The first quote appears under the subheading, “Starting points for an Amazonian holiness” (emphases mine):
It is possible to take up an indigenous symbol in some way, without necessarily considering it as idolatry. A myth charged with spiritual meaning can be used to advantage and not always considered a pagan error. Some religious festivals have a sacred meaning and are occasions for gathering and fraternity, albeit in need of a gradual process of purification or maturation (79).
This one is under the subheading, “The inculturation of the liturgy”:
[W]e can take up into the liturgy many elements proper to the experience of indigenous peoples in their contact with nature, and respect native forms of expression in song, dance, rituals, gestures and symbols (82).
Wherever Paul and his brother missionaries went, they taught the same truth and traditions. They did not attempt to “inculturate” indigenous religious practices with the gospel, but condemned them.