you can use any pan sizes you prefer, yes 2 8″ pans will work you may have leftover batter if they are 2″ in height (If you are using 2 boxes of cake mix) you can also bake white cake from scratch if you prefer. Depending on how you swirl the colors into the pan will determine how the result looks, don’t swirl too much or they will “blend” together and look muted, the orange is most prominent and I was sure to leave some white cake batter so the cake looked bright, I’ve seen this done with darker colors and it looks good too, it’s just preference really.