I wanted my pillow to look like a granny square on one side and have an X on the other side, so once the granny square was big enough to cover the front of the pillow I crocheted a wide (5 row) border of yellow and a 4 row border of gray, then seamed them together with gray yarn.
If you want to use the same colors/configuration I did, I started with a full skein of Red Heart Supersaver in cornmeal (light yellow), grey heather , and gold. I have almost all of the cornmeal skein left because I didn't use much in the pillow. The gray skein is almost gone, but it was smaller to start with. I used about 1/4 or 1/3 of the gold skein.
I bought a pack of two 16" throw pillows from Target because I didn't have any old throw pillows that I wanted to recover.
Here is the pattern that I did:
Here is what the back looks like (before I put it onto the pillow):