Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bow, combine butter with peanut butter, granulated sugar, and brown sugar until fluffy.
Add in the egg and vanilla extract, and mix until smooth. Add in the flour mixture, mix until it is fully combined. Add in the green food coloring until it is fully green.
Roll the cookie dough into balls and place onto a large ungreased baking sheet at least 2-inches apart. Bake for 10-12 minutes.