Combine flour, salt & baking powder into a bowl, mix and set aside.
In mixer bowl, cream together softened butter & sugar.
Once smooth, add eggs & vanilla-beat well.
Add the flour mixture to the butter / egg mixture a little at a time. Mix until the dough is smooth and flour is fully incorporated.
Remove 1/2 the dough & wrap in plastic wrap - refrigerate at least 1 hour.
With remaining dough in bowl- add several drops of food color & beat well until combined & dough becomes your desired color- you can keep adding drops & beating until you get to where you want.
Remove & wrap colored dough with plastic wrap. Chill in the refrigerator for 1 hour.
On a lightly floured surface, roll out each ball of dough separately to about 1/4 inch thickness.
Using a pastry brush, apply a little water to the darker layer of dough.
Roll the lighter color of dough around the rolling pin and transfer it on top of the darker colored layer of dough. The little bit of water will help them stick together.
Trim the edges so you end up with a neat and tidy rectangle.
Gently roll dough from one of the wider ends
Work log to even it out if the middle is thicker then the ends
Pour some sprinkles into your hand & brush the outside of the dough with a bit more water and add your sprinkles.
Wrap the dough in plastic wrap and refrigerate for an hour.
Once chilled, slice the dough into rounds to your desired thickness. The thinner the blade used to slice them, the better. A thick blade will tend to squish the dough.
Bake in the center of a preheated oven at 350 degrees for approximately 8-10 minutes