How do u make a two-toned cake...like just one cake, the top part purple & bottom part of it pink...just an example of colors.

Seems to me you'd have to make a white batter, separate it into 2 parts and color each one, then put in their pans.

Are you talking about the actual cake batter or the icing on the cake?

If you're talking about the frosting two tones........I would think the big flat icing tip would be your best friend there.

I thought she meant the cake itself......

Forgive me, but my computer shut down right in the middle of this reply so I had to start all over. If it's confusing, but you'd like to know more then PM me!

To get a neat two toned look you need to fill your piping bag first with color #1 then with color #2. Start in the center of your cake w/ a large flat tip. Pipe the icing while spinning your cake on a turn table. Once cake is completely covered then smooth it w/ a spatula. Decorate as you usually would.

Or for a different effect use tip 104 w/ the large opening side next to your cake. Use a quick side-to-side motion while piping the icing. For examples see these two photos: my icing was piped vertically, where as I believe you may want to pipe yours horizontally.

http://www.cakecentral.com/cake-photo_1202477.html
http://www.cakecentral.com/cake-photo_1198107.html

I've never tried this but read of a technique in which you ice the majority of the cake in color A ... then lay way or parchment paper over the icing you wan to keep, then ice the rest of the cake in color B. Kinda like using painters tape to tape off your woodwork when painting a room.

This is actually a 3 toned cake, but the same concept would work for 2 colors.

First ice bottom half in one color. smooth it with a paper towel and fondant smoother. Use a spatula to clean the edge( make sure there are no slivers of icing sticking out). Then apply the second. try to get close to the line, but leave an 1/8" gap. Go over second color with paper towel and fondant smoother when you smooth the icing it will fill in that gap. then lightly go over the whole cake with a paper towel and fondant smoother. Hope that helps.

Sorry I wasnt clear, but the picture above is what I'm talking about, thanks to everyone. I guess its the same technique with using two colors of fondant...