...how do I? Is it just striping the bag? TIA !

yes stripe the bag on the inside works great just be careful how much colouring you put on the stripe, you don't want it too dark

Thank you cashley!

I love the look of two-tone roses. I tried striping the bag and that just didn't work for me. I use two colors of frosting in the same bag, one on one side and the other on the other side (is that as clear as mud) it works great for me. Good luck

I prefer two different icings too. less messy