Preheat oven to 350°F. Spray two 8 inch and two 6 inch cake pans with baking spray and line with parchment rounds. Soak cake strips. Set aside.
In a medium bowl, sift together the flour, baking powder, and salt. Set aside.
In a measuring glass, combine the milk, oil, vanilla, and food gel. Set aside.
Beat the butter in a stand mixer until smooth. Add the sugar and beat until light and fluffy, about 2 minutes, scraping the bowl down as needed.
Add the egg whites one at a time, more or less, mixing until combined after each addition. Scrape down the bowl.
Add 1/3 of the dry ingredients to the mixer and beat until just combined. Add half of the liquids and beat until just combined. Repeat with another third of the dry ingredients, the remainder of the liquids, and finally the remainder of the dry. Scrape down the bowl as needed.
Wring out cake strips and wrap around the pans. Add 2 cups of batter to each 8 inch pan and 1 cup of batter to each 6 inch pan.
Bake for 28- 32 minutes. Check that each cake layer is done before removing it from the oven. The edges should just begin to pull away from the pan, the top will spring back when poked, and a skewer will come out clean.
Cool in the pans for 10 minutes before inverting onto a cooling rack. Cool completely before frosting and assembly.