* New colors are released frequently. OPI is constantly adding new shades to their collection, so any number given would quickly become outdated.
* Colors are discontinued. They also remove older shades from their line, making it hard to track the total number of colors ever produced.
* There are different types of products. OPI offers nail polish in various finishes (cremes, shimmers, glitters, etc.) and collections (seasonal, collaborations).
It's estimated that OPI has over 300 colors in their current collection. However, the number is always changing!