practiced making tints and shades of the three primary colors, three secondary colors and the tertiary colors. These color strings are very well done with watercolor. Mixing a range of tints and shades of all the hues in the spectrum is a wonderful practice. You'll learn a great deal about color mixing. Doing these studies will not replace your study of color from the live subject, but it will help to make you more familiar with your palette and the way colors interact with eachother.
Three of the tertiary colors