Dina,
My avatar is a split rail pattern and it has six strips in it. I wanted to make it purple and green, so I used the purple for the dominate/dark color, followed by a batik that had both that purple and greens, then used mediums to very light greens for the remaining strips. It is my understanding that you can use anywhere from two to however many strips you want. It is a very easy pattern, just be sure to lay it out correctly before sewing the blocks together. "Unsewing" is a pain!
Good luck!