It's possible our 10" of snow this week inspired all the white space in this card, but I know the Tim Holtz die was the starting point. When I saw it deeply discounted at my local JoAnn store, I knew I must have it for the Emphasize the Negative Space Challenge over at the Moxie Fab World blog. The challenge is one of several Cath is hosting to celebrate the release of Card Creations Volume 11.
The rainbow background was fairly easy and fun to make. I simply sketched the lines of the rainbow on a piece of paper and then cut various colors of cardstock to fit and fill up the die cut "window". The white layer is raised up on strips of thin cardboard rather than dimensional tape, which is sometimes a bit too thick for some designs.
Rather than extend the rainbow colors beyond the white layer, I matted it on a solid blue - like the sky. I think white-on-white would have worked just fine too.