Sugarloaf Rock Sketch, 8x10, watercolor
My oil painting students sometimes ask: How can you lighten color without adding so much white that the color turns chalky?
The first obvious answer is, simply, to use less white. I always first try to lighten my mixture by adding a light, tubed color. For example, I will add cadmium yellow to lighten a dark green. But sometimes this approach will change the hue more than I want. In this case, I'll use white cautiously. If the mixture loses saturation or warmth (both of which happen when you add white), I'll add a touch of some light, warm, analogous color.
Instead of white, some painters use a tint of Naples yellow. The problem with using Naples yellow rather than white is that your painting may feel a little too warm overall.
Another approach is to paint transparently on a white ground. If you use transparent colors, they will work like watercolors and give you rich color. I bet you've never seen a "chalky" watercolor painting! (I've included a couple of plein air watercolors from this week for your enjoyment.) Save your opaque paint for final touches and highlights.
Low Tide at the Duck Pond, 4x10, watercolor
Finally, you might try using zinc white rather than titanium white. Zinc is more transparent and will let some of the color's richness show through.
On another note, I want to mention the painter Xiao Song Jiang. His painting, "Tide," just won the Oil Painters of America's Gold Medal in the 2012 national exhibition. I was honored to have critiqued this painting for Song Jiang through Artists Network University. It is a pleasure to see such fine craftsmanship. You can see the painting here.