AI just saw a cake that was clearly stenciled, yet there were multiple colors in the design. Not only that, but it was done on buttercream! How did she do this? The colors seemed edge to edge and were perfect. I didn't see any stencil edde lines at all and it was a very large sheet cake...like 8 half sheets on one board. I can't find an answer!

AI don't think I can answer that without seeing a picture of what you're talking about. ;)

http://www.globalsugarart.com/video-tutorial.php?id=142

this is the cake.  The building part is an edible image, but the wording and logos are all buttercream on top of buttercream.  they were absolutely smooth.

AIt could have been done with an actual cake printer.

Like this one..

http://www.supplierlist.com/prod_img/cippan/69941_Chocolate_and_Cake_printer.jpg

Wow.  I didn't know this existed.  The cake was very very large....no way it could've fit through that hole....

It's a mystery!  But this thought comes closer.