I used 4 solid colors and 12 variegated colors to create the 4-patch units. Each took less than one skein of Red Heart or equivalent worsted weight acrylic (this is a charity blanket, so it needs to be machine washable and dryable by non-knitters).
To make one yourself, pick your 4 solids and 12 variegateds and pair them up compatibly (I put a yarn with some green next to green, one with some gold next to gold, etc. To be honest, I put some that were sort of similar too close together, so avoid this.) You can draw a little diagram to remind you of your plan, or just wing it, which is what I did.
Each square is fairly big. I cast on 51 for the first square, knit a row, then next row K24, K3tog, K24.
From there on, knit every other row, and knit the three center stitches together on the next row. You will end up with a square. End with K3tog. You can use any double decrease; just be consistent. I actually used slip 2 as if to knit, K1, pass slipped stitches over. That gave the distinct ridge.
From then on, attach squares to each other. On the first row, you'll cast on 26 then pick up 25 on the side of the previous square. Knit the first row (wrong side) and do a double decrease on the center 3 sts of the next row (your decreases occur on the right sides). Eventually, you'll only have to cast on for the first square in a row, the rest you pick up. I picked the middle stitch up on the middle between the two squares. Does this make no sense? Pick up a book on mitered squares and follow those instructions! Your squares can be bigger or smaller, too.
Hint: using the knitted cast on produces a very nice loop that makes it easy to do the picking up of border stitches.
When your blankie is as big as you wanted (for me, it was 48 squares or 12 4-patch units), use one of the solids pick up stitches on one long edge and knit a 4 garter-stitch ridge border. Do the same with the other long side. Then pick up along the edge of the borders and short edge and do the same. You can't avoid having a solid/border intersection that's the same color on the long side, but you can easily do so on the short side if you plan your colors carefully. Look at how I did it. Of course, you can make the border wider, but I wouldn't make it narrower. You should have enough of the solid color if you made yours the size of mine.
I think you could make a very sophisticated version of this afghan using more sedate solids and nicer yarn. I might even make one for our family room in shades of denim, gold and dark red.
I will be proud to donate this afghan to Project Linus. Leftover variegated yarn is being turned into granny squares for another charity project. I'll put a solid border around them all and it should be cute.
Next, though, I look forward to using the nice Marble yarn to make a crocheted project. Before that, though, I am going to go back to my nice Shetland yarn and Litla Dimun!
Want to learn more about mitered squares? Look into publications on modular or domino knitting. Here are some titles:
Domino KnittingThis is the first book on the topic I read. It has great practice potholders and such in it.
(whoa I pasted the info in from Ravelry and didn't know it would do the cover, too!)