Some of the first quilts I made were watercolor quilts and was totally fascinated in them. I have never tried the grid before, but used a book that shows how to do these in strip piecing. Its called "Watercolor Magic" by Deanna Spingola.
It is very easy to do and the quilts in the book are wonderful. I found its a great way to build your stash of fabric and learning values. Hope this helps.