If doesn't matter how old CorelDraw is, it worked for you and that is the main thing! I like the layout. Have you tried contacting Kona to see if you can get a few swatches from them? fabric.com had a link to swatches on their site, but it came up with a weird message. It might be worth contacting them, too.
Or you could take up dyeing to get your gradations for you background. 'Dyeing in Plastic Bags' by Helen Deighan is a good book and it can be great fun & addictive ;)
Thanks for suggestions. After little bit searching I found Fat Quarter Shop. They sell swatch cards of Kona cotton and some other fabric brands too. There are actual fabrics on those colour cards. I think I will buy that, it might be helpful for other quilts too. Dyeing is fun, but I have not done it for a long time. Maybe next summer I give it a try. It is such a messy, easier to do outside than inside.