Hi Dusty,
I'm not sure that I can tell you specifically what to use...it's all rather individual in terms of using what you like for glass...but I can point you to a few websites that may allow you to search on colors for the cat and the backgrounds. I tend to like opals for animals, which are not as opaque..but this pattern, which is lovely and drawn by Chantal Pare, gives the illusion of cathedral glass. I'd tend to use a couple of different ambers for the actual cat..one light, one for the darker points. As far as the background I think you could use whatever colors you like, the shading near the cat appears to be a shadow..I'd probably use something darker there as well. You might want to just go to your local glass shop and let the glass choose the project...I often do.
You can search on colors and types of glass at the following sites:
http://www.spectrumglass.com/stained-glass/products/product-search.asphttp://www.bullseyeglass.com/products/http://www.youghioghenyglass.com/stainedglass1.htmhttp://www.wissmachglass.com/glasssamples.aspxThat will at least get you started looking at samples...hopefully this will help!
De