Preheat your oven to 350°F. Grease a 9x13 inch baking pan or line it with parchment paper for easy removal.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the red and blue M&M's and white chocolate chips until evenly distributed.
Spread the cookie dough evenly into the prepared baking pan.
Bake for 20-25 minutes or until the edges are golden and a toothpick inserted in the center comes out clean.
Allow the cookie bars to cool in the pan for at least 10 minutes before cutting into squares.