After a quick Googling turned up very little, I thought I'd post here.
I used a Trader Joe's frozen strawberry as an ice cube in my seltzer water last night. Within 1/2 hour, the strawberry had paled (very light pink, to white at the tip) and my seltzer water was pink. The TJ package says "Ingredients: strawberries."
I don't have any fresh ones to try. The ones at the supermarket yesterday could have used some coloring to make them appealing... Is it standard to color commercially-grown strawberries? Was it the effect of the seltzer water? Anyone have any idea?
If it is food coloring washing off, I'm surprised it isn't in the ingredients.
And yes, next time I go there, I'll ask...but I was curious as to what you guys thought.