Wash the green and purple grapes thoroughly.
Dry them completely with paper towels.
In a large mixing bowl, combine cream cheese, sour cream, granulated sugar, and vanilla extract until smooth.
Gently fold the grapes into the cream mixture, ensuring they are well coated.
Transfer the grape mixture into a 9x13-inch baking dish.
Spread evenly.
Mix chopped pecans and brown sugar together.
Sprinkle this mixture over the top of the salad.