Which part of yellow cake batter gives it the yellow cake flavor? We recently made a cobbler by adding oil, water, and powdered yellow cake mix (from a box) on top of sugary fruit filling and it came of the oven crispy and delicious with that distinctive yellow cake flavor. What gives yellow cake its flavor? Even without the egg, this flavor is apparent, so it can't be entirely egg related, especially comparing yellow and white cake flavors.

UPDATE: 

It turns out this may be something of an inadvertent trick question. I have yet to test this but I get the idea that store-bought white cake and yellow cake batter powders both have a more similar cake battery taste than I originally suspect. The reason is pretty simple: the combination and ratios of sugar, salt, baking powder, and flour are probably not very different between the two powder mixes (don't be fooled by the yellow food coloring). Later, when the egg or egg whites and butter vs. oil are added it will of course affect the final cake texture but probably not the cake batter flavor.

Another possibility is that yellow cake batter mixes might have artificial butter flavoring whereas white cakes simply use vegetable oil for a lighter flavor.
Yellow cake made from scratch is given its color and flavor from egg yolks. A cake mix from a box, although you didn't add any eggs to it, might already have egg product in it. If it was one of the major brands of cake mix then it will likely have additives such as flavorings and food color to give it its distinctive flavor and color. In the homemade realm a white cake is made with only egg whites and a yellow cake is made with both whites and yolk.