If your jelly rolls have 42 strips in them (that's what I was figuring on) you are going to need to buy 2 more colored and one more white. It's too bad, because you will only be using 4 strips out of the 4th colored roll. But then you could maybe use the rest of the roll for a piano key border or binding or matching pillows or something.

I'm not sure on how much extra yardage, but to be safe I'd order another 2 yards (4 yards total) and if you have extra there it will be ok because you can always use white for something.