I'd use a warming (i.e. red) filter rather than a green. It might work. The problem is, assuming the iphone is using some sort of automatic white balance, the red filter is going to affect that white balance, so the results can be somewhat unpredictable. If there's a way to use a pre-defined white balance (e.g. tungsten, sunlight, etc.), you'll have much better success with colored filters, since the white balance is now set and works much more like film does.