Preheat an oven to 350 degrees. Line three cookie sheets with parchment or silpat.
In a medium-sized bowl, whisk together flour, salt and baking soda. Set aside.
In a blender or a food processor, pulverize strawberries into a powder. Sift through a strainer to remove any large pieces.
In a large bowl, beat the butter for two minutes or until light and fluffy. Add in sugar and beat for an additional two minutes. Add in egg plus egg yolk, along with the vanilla and beat on medium until well incorporated.
Add in flour mixture and blend just until dough comes together.
Remove dough from bowl and divide into three equal portions. Add one portion back into the bowl and add the strawberry powder and the food coloring (if using), mixing until incorporated. Remove strawberry dough and set aside. Wipe out bowl and add second portion of dough, along with cocoa powder, mixing until incorporated.
Pinch small portions of each color of dough (about 1/2 ounce each) and roll together to form a ball, keeping each distinct color. Roll in sprinkles or sugar if desired.
Bake at 350 degrees for 10-11 minutes. Cool completely on wire rack.