How can I tell a friend not to have her daughter wear a white dress to my daughter's first communion party?

Q: When my oldest daughter made 1st Holy Communion, our close friends brought their girls to the party in big white dresses. I was slightly offended and some of our guests made comments about it. This year our 2nd daughter is making Communion with one of the aforementioned girls; same day, same church. Our party is after the church and theirs is a week later. How do I politely ask them not to bring their daughter in her Communion dress to our party? Is this rude? Can I avoid a double Communion party?

A: Why not just take a direct honest approach? Try something like "We know this is a big day for each of our girls. Would you be willing to have your daughter wear a different color dress at our communion party so it's obvious to all the guests, who's communion we are celebrating? I am planning to have my daughter where a blue (or whatever color you choose) dress to your daughter's event. This way, each girl will have there own day to feel special."