When choosing a fabric, the pattern doesn't matter as much as it having the colors you want, right? Because you won't see the pattern anyway. Is this right? I haven't made one yet and have a book ordered, but was looking at some on this sight.

When I choose fabric for a stack n whack I like to make sure there is a repeat of about 12-14 inches. Make sure there is not a lot of open space in the design and you don't want it all too close either...good luck...they are super fun to make! I should add also that if your repeat is bigger than 14 inches you usually need more fabric.

You can go to the sections here with all of these quilts, many have posted the original fabric.
Compare how the blocks/quilt looks and determine which fabric styles you like the looks of best :D:D:D

Like DeeBooper said. You want a pattern without a lot of 'flat' background. If you ordered the OBW book, she has a lot of info on fabric choice. And rather then a set yardage, you need to purchase a number of pattern repeats. Again all covered in the OBW book. I don't have the Stack & Whack book, but I'm guessing it covers the same info. they are pretty easy and lots of fun, not to mention addictive!

If you are making the 8 point "stack n whack" you will need 8 repeats of the fabric. I recently found a Kona floral with an 18 inch repeat and we were able to us the other side of the length also. What you need is 8 identical pieces of material. Take your time in the shop and lay it out, see if you can use the "backside" without too much waste.
Anything in the fabric could be the focal point of a star. I once saw the bees hidden in the fabric become the center of the star. It was gorgeous.

the colors don't matter- the design repeat is what is important- since you have to cut everything exactly the same repeat- to make your blocks. any color will work- busy designs are usually used- look at pictures of peoples quilts-and the pictures of their starting fabrics you will find the most successful ones are very busy fabrics.

Another point to consider is good contrast. Unless of course you are trying for a subtle look, which can be gorgeous as well.

which one of these are you going to make?
You have three different patterns although Kaleidscope and Stack N Whack are basially the same.
Althugh The Stack N Whack an be several patterns.
Having said that, all look best in bold patterns and color.
Small designs don't work but needs large and bold with patches of color. If you want to try it take one of the hinged mirrors and check the design.

And when selecting fabric, be sure and get what the pattern or design calls for in the number of repeats.
Repeat designs should only be considered down the selvedge edge. Although there is a strip of repeats down the center, they don't always match up with those along the edge. The center ones can be used for another set of blocks depending on the pattern.

You need the multiply repeats lengthwise because side-by-side repeats are not identical. I did one with eight repeats once using side-by-side. I alternated the pieces to make the design look intentional & not an 'oops'.