Preheat oven to 350°F.
Flour and butter bundt cake pan and set aside.
Cream butter and sugar together in stand mixer on medium-high to high for 5 minutes.
Meanwhile, combine flour, baking powder, baking soda, salt, and vanilla in small bowl.
Turn speed on mixer to medium. Add eggs, one at a time, to bowl. Let mix for 30 seconds before adding next egg.
Turn speed on mixer to low. Add 1/3 flour mixture. Add 1/2 cup buttermilk. Add second third of flour mixture. Add remaining buttermilk. Add remaining flour mixture. Let mix until just combined.
Divide batter into four bowls. Add coloring to each and mix with a spoon until combined. Layer batter into bundt cake pan, one color at a time.
Bake for 50-55 minutes until cake tester comes out clean.
Let cool for one hour on cooling rack with opening facing ceiling (batter side up).