I began this experiment with my recent cloud watercolors in mind (Watercolor Clouds from Photograph, Watercolor Painting Process – Clouds). However, instead of using gray-on-gray, I used two different colors. I laid down the dark red first. Then I used a diluted red and copied the dark contour, leaving a white gap. I chose blue to surround the lighter red and to underscore the darker red. I was hoping to merge the blue pools with the red to gain a purple interface. The dark red pool overflowed. Evidence of the rivulet extends from the red-blue blob to bottom of the paper. I completed the background by filling in both sides of the red drip with blue.
I wanted this piece to have some depth to it, so I applied a graded wash to both sides of the red line: