No rule for this one
No ending or word group predicts the article of Jeans. Learn it as a pair and say it out loud: die Jeans.
die Jeans
It's die Jeans. Jeans is feminine.
Die Jeans ist blau.
The jeans are blue.
No ending or word group predicts the article of Jeans. Learn it as a pair and say it out loud: die Jeans.