Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large bowl, beat the softened butter, granulated sugar, and brown sugar together with an electric mixer on medium speed until light and fluffy, about 2-3 minutes.
Beat in the egg and vanilla extract until well combined, scraping down the sides of the bowl as needed.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry mixture to the wet mixture, mixing on low speed until just combined. Do not overmix.
Gently fold in the red candy, blue candy, white candy, and chocolate chips using a spatula until evenly distributed.
Scoop rounded tablespoons of dough (about 1.5 inches in diameter) and place them 2 inches apart on the prepared baking sheets. Bake for 10-12 minutes, or until the edges are golden brown and the centers are still slightly soft.
Let the cookies cool on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely. Arrange on a parchment-lined platter or board for a festive display.