Yes, it is possible.
It all depends on the surface mapping within Metasequoia (the modelling environment). The colors you see on the model are mapped as a texture onto the surfaces. This texture is made out of a BMP-image, which I created in a normal graphics program (e.g. Paint/Photoshop/PaintShopPro, etc.).
At the moment the wings upper and lower side are mapped (that the technical term for applying textures) with the same texture, so they look equally.
If you want to change that you have to do 2 steps:
1. create or modifiy the BMP-file so that it has color schemes for wing top and bottom.
2. in Metasequoia select the polygons of the upper side and use the map function to apply the BMP-file to it and move it until it fits. Do the same with the bottom-polygons of the wing.
Of course - if you get stuck somehow, you can send me some pictures of your real model and I'll create a very special "personal edition" of the Scanner
But maybe you want to try it on your own to get some experiences in Metasequoia.
Would be great if you could send me then the result
Btw.: I sometimes use FMS/Metasequoia to test the color finish of my real models. That works fine and you get a very good impression how your model will look like
before you do the finish.