Mix graham cracker crumbs, sugar, and melted butter in a bowl until the texture feels like wet sand.
Spoon about 2 tablespoons of the crust mixture into each 6–8 oz jar. Press gently to form an even base. Set aside.
In another bowl, combine sweetened condensed milk, sour cream, lime juice, lime zest, and food coloring (if using). Whisk until smooth and creamy.
Divide the lime mixture evenly over the crusts in the jars. Smooth the tops with a spoon.
Refrigerate for at least 2 hours—or overnight—for the filling to set and flavors to develop.
Right before serving, beat heavy cream, powdered sugar, and vanilla in a chilled bowl until stiff peaks form (about 3–5 minutes).
Top each jar with whipped cream. Garnish with a lime slice or curl of zest, then serve chilled.