Ah, if it's a mix then it probably will come out that color because it's genetically engineered to come out that color (but I still think the pic was PS the heck out if it). Just look at the entire panel of "ingredients" that go into that tie dye cake on the box! So yeah, I guess you have no worries there.
I, yes, me, recently bought the zebra Duff mix because it was on sale for $2 at the store, I normally see it for $8+ and I'm a scratch baker so no way would I ever spend $8 on a mix let alone $2, but long story short I bought it and made it - my advice - make sure if you want a 3 layered cake like the photo you buy 3 mixes because my 1 mix barley made the suggested single pan of 9" round. And since I didn't read the instructions at the store I missed the part on the box saying it "makes 1 pan of 9" round". I guess you are just supposed to forget that the photo on the front shows 3 layers. HAHA anyway no way could this thing be torted to 3 layers. I tried to tort it to 2 like I always do with my cakes but because it's a mix (and I'm not used to that) it was really soft and totally crumbly.
So I revise my advice: if you want your cake to look like the photo on the box - you need 3 mixes perfectly baked, torted to 1" high with an abgay, a quick icer and a ruler to put exactly 1/4" of buttercream on it, a fondant sheeter to roll your fondant to the perfect thickness (using Duff fondant, of course haha) and a pasta roller to do the dots and roll them to the perfect exact same thickness. Then Photoshop the photos to clean up all the crumbs and uneven bits in the photo using at least a $2000 DSLR camera using a 50mm lens.
I am seriously only writing this because what is on the cover of the box of practically anything you buy is not what you are going to end up with at home.
I wish you the best of luck! Perfection is possible, but like I said you need patience and the right tools.