Preheat oven to 325°F (163°C).
Mix graham cracker crumbs and melted butter. Press mixture into the bottom of a 9-inch springform pan to form the crust.
In a large bowl, beat cream cheese, sugar, and vanilla until smooth. Add eggs one at a time, mixing well after each addition.
Blend in sour cream and fold in half the M&Ms.
Pour the filling over the prepared crust and bake for 55–60 minutes, or until the center is just set.
Allow the cheesecake to cool completely, then refrigerate for at least 4 hours or overnight.
Before serving, sprinkle remaining M&Ms on top for decoration.