The traditional and most common support--material to which the paint is applied--for watercolor paintings is paper. Other supports include papyrus, bark papers, plastics, vellum, leather, fabric, wood and canvas. Watercolor paper is often made entirely or partially with cotton, which gives a good texture and minimizes distortion when wet. Watercolors are usually translucent, and appear luminous because the pigments are laid down in a pure form with few fillers obscuring the pigment colors. Watercolors can also be made opaque by adding Chinese white.

What's the best answer to this question: is white color uses in opaque water color?
yes