I did a good bit of layering last night and was able to get the first cat's fur color toned down and deepened. I also added a darker gray around the white areas to bring those out and add some shading. I still have some tweaking to do, but I really like where this is so far.
For the second cat, I started with the beginning layer of color, so I'm looking forward to getting that to a more finished point. In the end, I will need to add some color underneath both cats so they don't look like they are floating on air. :)