Sesame Street Cake

This is modeled after a Sesame Street puzzle I saw on the internet. I couldn't copy it exactly. I almost pitched the cake out the back door a few times but was talked down by my hubby thankfully. It's not the neatest but I thought it gave it a whimsical look. MMF characters and a mix of MMF, Royal Icing pieces and butter cream form the buildings. Saw a little too late that the RI was not necessary. Most importantly my 2 y/o daughter loved it. Could someone tell me the best way to color MMF??