Beat the butter on medium speed until smooth and creamy. Then add brown and white sugar and mix again on medium speed until light in color and fluffy.
Add in the eggs and vanilla, and scrape down the side and bottom of the bowl as needed. Continue mixing.
Add the baking powder and gradually add the flour, one cup at a time. Beat in low speed and slowly adjust the speed to medium until combined.
Using a spatula, fold in the mini chocolate chips, followed by the brown, green, and red M & M's minis.
Take a small spoonful of dough, (use 1 tablespoon) roll it into a ball then press the ball down slightly on the cookie sheet. If you have M & M's and chocolate chips left, press a couple into the top of the cookie ball. Bake the cookies between 9-11 minutes in the preheated 375-degree F oven until they are golden brown on the edges and bottom.
Remove from the oven and allow to cool on baking sheets for 5-10 minutes. Then carefully transfer to a wire rack to finish cooling.