Beat the butter with an electric mixer until fluffy, then add the sugar and beat for 2 minutes. Add the vanilla and beat until combined. In a separate bowl, combine the flour and salt, then add this to the butter mixture.
Shape the batter into a ball, then divide into 4 pieces. Dye the pieces green, red, orange and yellow. Flatten the dough into disks and stack them on top of each other, then slice them in half and roll into 2 balls, swirling the colors together. Wrap the balls in plastic wrap and place in the fridge for 1 hour.
Roll the dough out on a floured surface until it is 1/4-inch thick. Cut out leaf shapes and transfer to a baking sheet lined with plastic wrap. Make indentations with a butter knife to create the veins of the leaves. Refrigerate for 30 minutes until firm, then bake at 325F for 15 minutes. Cool completely and enjoy!