It's gorgeous! I would definitely leave the greens as they are. Having a more toned green (i.e. it contains a bit more grey) in the background than in the foreground means that it adds depth to the quilt, giving something of a 3D effect (in a good way). The foreground green is brought forward, focusing attention on whatever you are going to have in the white square-on-point in the middle. The background green certainly doesn't blend in with the purples at all, they're perfectly well distinguished.
I am absolutely salivating over those batiks, especially the elegant curves of the background green one.