how do I get the rainbow effect in my batter without it all mixing together?

Found a tutorial here: http://www.omnomicon.com/rainbowcake HTH.

Ashley

this was what I imagined it to be; just wasn't sure how to go about it. thanks!

That's a great tutorial! I did rainbow cupcakes and found it was really helpful to separate each color into it's own little ziplock then just snip the tip and you have little batter piping bags, way easy and less mess than trying to measure out colored batter.

If you use light (or white) and dark chocolate batter for the stripes, it's called a zebra cake.