How do you say I have red hair in French?

There are a couple of ways to say "I have red hair" in French, depending on the nuance you want to convey:

Formal/Neutral:

* J'ai les cheveux roux. (This is the most common and neutral way to say it.)

Informal/More descriptive:

* J'ai des cheveux roux/rouges. (You can use "roux" or "rouges" for red, but "rouges" is slightly more informal.)

* Mes cheveux sont roux/rouges. (This emphasizes the red hair, highlighting its color.)

More poetic/Literary:

* Je suis roux/rouge. (This literally translates to "I am red," but it's a poetic way to emphasize the red hair as a defining characteristic.)

The best option will depend on the context and your desired level of formality.