Preheat oven to 350 degrees. Lightly spray a 9x13" pan with non-stick baking spray. Set aside.
In a large mixing bowl using a hand or stand mixer, cream together the room temperature butter, granulated sugar and brown sugar. Add in the vanilla and eggs, mix together until smooth and fluffy.
In a separate bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stopping the mixer occasionally to scrape down the sides of the bowl with a rubber scraper. Once all the ingredients are combine, the dough will be thick and smooth.
Using a rubber scraper or wooden spoon, fold in the M&M candies, chocolate chips and white chocolate chips to the batter. Mix until just combined.
Spread the batter evenly into the bottom of the prepared 9 x 13" pan.
Bake at 350 degrees for 35 minutes or until the bars are golden brown and just set in the middle. Be sure to not over-bake.
Remove from oven and let cool to room temperature before cutting into squares.