I would paint the house a dark brick red, or even a tree brown. Shades of grey or smokey white would also go well with a house with a forest green roof. This though also depends on the surroundings is the house in a forest? Are there other houses around this house? What color are those houses? Depending on the surroundings of the house the above colors could be awkward. The trim of the house also would influence the color of the paint. I would recommend a darker trim and a lighter base color. For example if you go with the tree bark brown make it light on the majority of the house outlined on the trim with a darker shade of tree bark brown. This emphasizes the edges and the size of the house.