How are your drawing skills? Although it is very handy to learn good drawing skills before painting, being able to copy existing sketches will do just fine for this lesson. Get good definition around the eye during this phase, which is easier to maintain than to create in the later phases.
I suggest drawing your cat on regular drawing paper first. Then once your drawing is complete, transfer it to watercolor paper. Be sure your drawing is detailed enough to see the eyes, nose & mouth clearly. For the best result with watercolor, paint what you know by heart.
Wet soft foundation color
Colors used: French Ultramarine Blue & Burnt Sienna
Start by mixing a paddle of French Ultramarine, next rinse your brush and then mix a puddle of Burnt Sienna. Mix equal parts of each color together to create grey. Mix more French Ultramarine than Burnt Sienna to get a cool grey. More Burnt Sienna then French Ultramarine to make warm grey.
Allow each step to dry before applying next step of paint.
Detail Eyes, Nose, and Mouth
Eyes first. Fill in the iris color with the color orange or green. Be sure to leave the highlight by painting around the unsketched white area carefully. Next using a dark grey mix with a small liner brush and a round brush, paint the eyes around the outside and the detail of the iris be sure to leave the white highlight.
Fill in nose with wet, softened-down Alizarin Crimson to outline the nose and the mouth.
Detail the stripes using a dark, warm, grey. Work over some stripes using the same colors as before, but now you will be using a darker value. Dry completely between adding more layers.
Keep layering, from lighter to darker values, until you achieve the desired affect.
Add more stripes
For variation, add new stripes as well as going over the lighter ones with darker values. Do not use black (see finishing phase).
Once dried completely, mix French Ultramarine & Burnt Sienna (not black) to add the final detailing in some stripes and around the ears.