Because I am working in encaustic I can't work with those materials in the group, so I bring a sketchbook and egg tempera paints. Sometimes I just mess with colors, and other times, like yesterday I started drawing with pencil.
First I drew the two yellow triangles and studied them. The parallel lines of the long sides invited thought. So I extended them. Then I drew the vertical and horizontal lines away from the leftmost point of the left triangle. At that point I wanted a frame, so I drew the enclosing square. That enclosure created most all of the negative space (the red ochre and Prussian blue). I then drew the arc at the bottom of the right triangle and knew I was done with the drawing.
I painted the two triangles first, left in yellow ochre, the right in Indian yellow. Then I drew what I knew would be the central focus of the image--the Vermilion diagonal. Next came the red ochre, and after that, the Prussian blue. Then I filled in the green rectangle (Indian yellow with Prussian blue). I knew the small almost triangle near the arc would be black, but the arc gave me pause. I eventually chose a blue green from a different mixture of Indian yellow and Prussian blue.
Only in considering the arc did any "thinking" go on. Each shape became its color without thought. I can't explain how this happens. But when I set it on a window sill to step back from it, I knew it worked. And, I can't explain how I know that either. And at this point, I don't know if the color of the arc will change when I move it to encaustic.