This is a cake that Sistergldnhair and I thought of. It is a cake that we dyed to look like tie dye.

Step 1: Materials

What you will need:
A large bowl
A box of Pillsbury white cake mix
Red, Blue, Green, Yellow food coloring
6 small bowls
Spoons
3 Eggs
1/3 cup of vegetable oil
1 cup water
A 9x13 cake tin
Any kind of frosting you like
Toothpicks

Step 2: Mixing the Batter

Pour your batter, eggs, oil, and water into your large bowl.
Stir the ingredients in the bowl together.
As equally as you can, divide the bowl of batter into 6 small bowls.

Step 3: The Colors

Get out your food coloring.

(these are the number of drops of food coloring in each bowl)

Bowl one: 7 drops of red. 2 drops yellow. This is red.
Bowl two: 5 drops of yellow. 4 drops of red. This is orange.
Bowl three: 7 drops of yellow. This is yellow.
Bowl four: 7 drops of green. 2 drops of yellow. This is green.
Bowls five: 8 drops of blue. This is blue.
Bowl six: 5 drops of blue. 4 drops of red. This is purple.

These are your six colors.

Step 4: Tie Dye

Now is the fun part.
Take your first bowl of batter and pour pieces of it all over the cake pan, like in the second picture.
Repeat with all the other colors.
Try to use as much batter as possible and get the batter as even as you can.
Now take out a tooth pick and swirl around the colorful batter as much as you want.
Eventually your batter will look like the main image.

Step 5: Baking

Set your oven to 350 degrees F.
Let it warm up for a bit.
Once your oven is ready, put you cake in the oven.
Let it bake for 15-18 minutes, checking it occasionally.
It will look really cool once you take it out.

Step 6: Frosting

Frosting your cake in optional, but I think it tastes better with frosting.
Once the cake has cooled down, pour the frosting on the cake.
Using a butter knife, spread the frosting evenly over the cake.
Smooth out the frosting.
You can color the frosting is you want to.