I apologize in advance for the photos. On my phone the colors looked really dark, when I posted them, they looked really light. Please enlarge so you can see more clearly strokes and the effects of smearing. My own Julie flat cat was very cartoon like, but I'd like to show you how to use pastels.
I've smeared to blend some areas then gone over with large sweeping strokes in white. Strokes should flow in the direction of the fur. Experiment with varying the pressure, use less, more, or starting out heavy and ending light.
I could end it here, but its not the 1960's
I've taken my meds and they've kicked in.
This is the final product. I've added some grey around the eyes and a few strokes. I could continue refining it by working on the whisker holes on her whisker humps and a few other areas, but I think you get the general idea.
By starting with blue and purple, I wanted to show you how easy it was to change the entire look of your kitty so you wouldn't be afraid to experiment and try new things. I almost never use black. I think you get a much richer look by using other colors. I block out the darks first, then start adding color. Think of and follow the bone structure under the fur. When doing your kitty, keep your strokes flowing in the direction the fur grows. The softer areas you can add color with your finger tip.
I think next I'll talk about finishing, then come back to coloring tabbies, unless you want tabbies first. Let me know in the comments. Do you have any particular question? I will be covering eyes after tabbies.
My Julie flat cat wasn't nearly as detailed as the head I did above and more cartoon like, I wanted to give you an idea of the range of techniques you could use.