Here's his cake:
We did the inside in camo:
We could barely find it to eat it! LOL
Anyway, to get this effect I just colored vanilla cake mix and then put it in the pan in plops of color. I went over the colors to make sure the batter was deep enough in the pan and kind of mushed it around a little. I didn't really swirl it because I didn't want the colors to blend.
I saw a picture on pinterest of some pans with the batter, and this is what I figured out to do to get the same effect.
Dax thought it was pretty funny.