Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, mix together butter and sugar until fluffy. Add in the eggs and vanilla extract and mix until smooth.
Add in the flour mixture and mix until it is fully combined. Press the cookie dough into a greased 9x13-inch baking dish. Bake for 25-30 minutes. Let cool completely.
In a large bowl, mix butter with powdered sugar, milk and vanilla extract until combined. Stir in the food coloring. Spread frosting onto the cookie bars and decorate with sprinkles.
