I've made a couple of McKenna's quilts, but not this one. My fabric kits had stickers on each cut piece identifying it by number and color. Go to her web site,
www.pineneedles.com, select "Fabric Lists", and click on "Wind in the Whiskers Fabric List." On the second page you will see the background fabrics for all 7 blocks. Are you able to identify the background fabric from this? I think she usually uses the sky fabric as the background for each block. A double check in your case might be to see if the measurements of the background are the same as the individual block.
Also note under "Corrections" that there are 3 for this quilt, and that there is a toll-free number to call under "Contact Us" if all this doesn't answer your question.
Don't mind this minor bump in the road--you will have a fabulous time making this quilt!