I often go to the manufacturer's website and look at the different fabrics in the collection that interests me. They usually have the print number AND the colour number listed with the fabric photos. Then I can do a Google search using the the manufacturer's name and the complete series of numbers for the fabric I want.
This really made a difference when I was looking for co-ordinating fabrics for the quilt I am working on. Because the line was a couple of years old, I ended up buying from three different shops.