Beat the butter and sugar together in a bowl.
Add the egg yolk and vanilla extract and beat the mixture until it is smooth.
Next, add the flour and salt and mix everything together to form a soft dough.
Divide the dough in four. Color one piece brown by kneading in cocoa powder. Color another pink with cranberries and food coloring. Leave two plain.
Wrap the dough in plastic wrap. Put it in the refrigerator for about 30 minutes. Preheat the oven to 350 degrees.
Roll the dough out on a floured surface. Each piece should make a rectangle about 7 x 8 inches.
For rolled cookies place the plain dough on the chocolate dough. Trim the edges and roll into a log. Repeat with the pink dough.
Marbled cookies are made from all the dough trimmings. Simply knead them together, then roll them into a log.
Slice the log into ¼-inch slices. Put the slices on nonstick or lined baking sheets.
Bake your cookies for 15 to 18 minutes or until lightly golden.