100% Buttercream~ I frosted entire cake in white BC. Then I took one or two different shades of green and put small amounts here and there on bottom 1/2 of cake and smoothed. then I put some brown and golden yellow in smaller amounts usually with a small spatula or #2, 3, or 4 tip here and there… then smoothed again.
for top half of cake. I just added a couple of shades of blue in same manner.
I outlined tractor (I do not have a cake copy machine, so I free hand it with a toothpick before outlining and filling in, w/ icing. Used #4 tip in black to outline tractor, and larger tip (#6, #8, or 10) to fill in tires, smoke stack, and any other areas in black….and smooth w/ finger dipped in very warm water.
I made #3 track marks on tires.. and I have to go back over entire tractor details after filling in all colors to make detail stand out in #3 or 4 tip black.
I used #10 tip for fence and grass tip for base of fence and bottom of cake above boarder. #4 tip for writing message in yellow. Leaf tip #352 for boarders.
hope you enjoy re-creating~ :)