I posted this in the other thread, but I will post it here. It is about an online tool that I use all the time to match to exact Kona (or Bella, Aurifill, etc.) colours.
There is a website run by a quilter who is also has a degree in computer science. Her site is
www.play-crafts.com. She invented a tool that she calls Palette Builder, and you can access it on her website. You upload the photo with the colours that you want to match, and select spots in your picture. The program will give you the shade of Kona (or whatever option you select) that matches the colour in the picture. Maybe that will be helpful for you? I have used it myself many times and it is a wonderful tool.
This is the direct link:
http://www.play-crafts.com/blog/palettebuilder2/