I don't know what girls wear in Europe.  But it's quite possible that someone saw girls in pink tights on stage (or even in class) and thought they were white.  I've just never heard of anyone other than men wearing white tights.

You can get all different colors of tights because: 1. Some people choose to wear non-standard colors in class. 2. Costumes frequently require non-standard colors. 3. Black is a very popular color, and makes its way into class a LOT. 4. Men sometimes buy these tights, and they might want a different color in class than pink. 5. The tights may be used for non-ballet dance activities, where other color schemes are desired. 6. The tights may be used outside the dance studio altogether --- some people prefer dance tights to standard "fashion tights" for everyday wear.

That said... I've found that pink is by far the easiest color of tights to purchase (unless you're buying specifically men's tights).  White IS available, but not in all sizes and styles, and it often must be special-ordered.

White looks kind of pink anyway, if you have pink-colored (white) skin and the white tights aren't too opaque.  And pink looks kind of white.  It's a subtle difference between the two.