Separate equal parts of the dough into different bowls, or onto a large platter. Separate as many parts of dough as you will be coloring the dough. Ie: if using all 6 colors of the rainbow, separate 6 equal dough parts.
Add 2 to 3 drops of one food coloring into the first dough ball and use your hands to mix in well. I recommend using food safe gloves to keep hands from staining.
Roll colored dough piece length wise and inside a large bowl. Repeat above steps with each color and lay each colored piece against one another until done.
Use a 3 tbsp ice cream scoop and begin to lightly scoop the dough from one end to the other. You only want to lightly brush the surface so you are able to pull in all the colors. Place on baking sheet at least 2" apart.
Repeat until no more dough remains. If you do have some remaining dough as you clean off excess, place in a separate bowl for afterwards.
For the remaining excess dough, combine in bowl with only a few folds and gently so not to blend the colors together too much.
Scoop dough with 3 tbsp ice cream scoop and place on baking sheet at least 2" apart.
I recommend baking the cookies to the recipe you chose. A lower bake temperature (350 F) is ideal to ensure the colors do not darken much.
Allow cookies to cool before enjoying.