Fabrics & Transfer Tools for Sashiko

What makes a good fabric for Sashiko stitching? It will need to have a weave that can be hand stitched easily.  I look for a good quality natural fibre fabric that has some texture. How much?  That depends what I plan to do with it. Does it need to be navy blue? Absolutely not. Indigo blue is the traditional colour Sashiko designs were stitched on but the reason was practical. It was the dye colour available at the time. And white stitching on dark blue is timelessly beautiful.