1. Select a base color (maroon), a highlight color (cream), and a shadow color (dark blue). For this tutorial, I used the Selection tool and Fill tool to create a simple circle shape with the base color. Decide where the light is coming from, paint the side of the circle nearest the light source with the highlight color. Paint the opposite side of the circle with the shadow color. For painting I use a Photoshop default brush - the spackle brush, at 100% opacity. Obviously, painting at 100% opacity produces hard edges where one color meets another. The next step is to fade or blend the colors into one another.

2. To start blending two colors, select one color - in this case, the highlight color. Set the brush to 30% opacity, then paint along the hard edge where the highlight color meets the base color. Our goal is to achieve the  3-dimensional quality of a sphere so paint in curving strokes as indicated by the white arrows in the figure.  Apply the same steps to the shadowed area.

3. Painting with the brush at 30% opacity produces a highlight-base mixture and a new leading hard edge. Pick this color and repeat the process of painting along the hard edge where the two colors  meet. Use the same curving stroke following the shape of the sphere.

4. After several repetitions of Step 3, more and more of the hard edges will have been painted over and the surface now starts to become smooth and obviously spherical.

TIP: With the Brush tool selected, you can switch from the brush tool to the color picker by holding down the Alt key (Ctrl for Mac).

5. Continue repeating the previous steps until most of the hard edges are no longer apparent.

6. For an even smoother finish you can begin to paint using a swirling stroke instead of a curving stroke as shown. But remember to confine the highlight color to the area that catches the greatest amount of light.

7. Once you are satisfied with the degree of smoothness that you have achieved by many repetitions of the blending process, you can paint in a pure white spot on the highlighted area. This makes the surface seem shinier and slightly reflective. For smoother surfaces, these highlights are more well defined and less blurred.

And there's your final product!

You may ask, why not simply use the blend tool in Photoshop? You could, but the Blend tool produces surfaces that look too artificial. The blending technique described here affords more control and approximates blending using actual paint. It produces interesting textures that look more natural or painterly depending on your brush stroke.

M.