To make a simple change and balance it out a little more, cut off about 1/2 side to side where you have the green and purple stripes without white and attach those to the other end where the stripes are white and purple. Leave the one green stripe (amongst the white and purple "row") where it is. Just as individuals are, quilts can be unique too. You could do a piano key border in the purple, greens, and white and then either bind it with a green or purple. Or you could just bind it with a scrappy binding using all the purples, greens, and white. Look forward to seeing what you wind up doing. I am sure your son will love it no matter what you do to finish it up - cause his Mom made it just for him.