I will be making a cake where 1/2 is one color fondant, and the other 1/2 is another.

I have never had a request for a cake like this before and my plan is to roll out each color, trim an edge straight on each, run a very thin swipe of water down the edge of 1, overlap very slightly, press together and transfer onto the cake.

Is this how any of you do it or am I way off?

I would really appreciate any tip or tricks you may have.

I have a fondant swag what will drape and cover the seam but I would liek to have it as clean of a seam as possible where the 2 colors meet when the swag is removed to cut the cake.

Help!

Thank you

That is exactly how I did the following cake:

http://www.lamaisondesgateaux.blogspot.ca/2011/01/blanc-au-rose-ou-rose-au-blanc.html

I overlapped the seam between 1/2 and 1/4 inch.  Mine wasn't a straight line between the two colors, but the principle is the same.  Wet the edge of the bottom fondant a bit, then roll it a bit to ensure a good bond.  That way it won't separate at the join when you move it to the cake.  If you are covering the join with a swag it won't really matter if your join is perfectly straight.  You might also want to place the darker color on top so that you don't get the darker color bleeding through at the join when you roll it.  On my first go I had the white over the red and as I rolled it the red started to show through the white.  With the red over white it wasn't as noticeable.

hth

 Your cake came out beautiful!  I'll be giving this a shot Saturday. 

Sometimes I get it all figured out in my head but then I do it and it doesn't quite go the way I had envisioned :)

Thank you so much for your help!

Glad to be of help.  Make sure you let us know how it turns out.