Preheat the oven to 350°F and line 2 baking sheets with parchment paper or spray with non-stick spray. (To get best results, use parchment paper)
In a medium bowl, whisk together the flour, baking soda and salt together.
In another large bowl, using an electric mixer at medium speed, beat together the butter and sugars until smooth and mixed together well.
Add the egg and vanilla and mix on low speed until mixed in.
Add the flour mixture and mix in until just incorporated. At this time you can add chocolate chips right into the dough or wait to add them when you mix the colored dough up. (We did some of the colored dough with white chocolate chips and some with semi-sweet chocolate chips and then added some extras on top before baking them. )
Once the cookie dough is made, You just divide the cookie dough it into 3-8 portions depending on how many colors of the rainbow you want in your cookies.
Using food coloring, color the doughs as desired by adding food coloring to dough and stirring together. You can do these as dramatic or pastel as you like.
Roll each colored dough into approximately a 14-15 inch rope. Then, place each colored rope next to each other on a large piece of parchment or cling wrap. Wrap up tightly, pressing the doughs together forming a log and twist a bit.
Remove the wrap and cut into 1/2 inch or 2-3 tablespoon portions.
Roll portions into balls adding more chocolate chips on top and place onto the prepared baking sheet 2-3 inches apart.
Bake for 9-13 minutes depending on size or until the edges are set without overbaking. Take them out of the oven a minute or so before they are completely baked to get the best texture!
Allow cookies to cool on the baking sheet for 5 minutes and then transfer to a wire rack to cool completely. Check out the rainbow!