If you're using fruit that browns easily like bananas or apples, either cut them just before assembling and serving, or you can lightly brush them with a bit of lemon juice. You can also opt for types of fruit that doesn't brown as easily- of the fruits I'm using here only the banana is going to be an issue, so my personal preference would be to swap that for pineapple or mango if I was making it as a party platter.