We're studying warm colors this week. They're my favorites. Last week was the scourge of the cool colors - blue bores me, purple scares me and green? That's for beans. I will use certain flavors of redviolet and yellowgreen. I'm not rigid.
So the point was to identify and use only warm colors in a drawing. Draw with heavy crayon marks first, then paint with watercolor. The crayon is a resist. You can paint right over it and the line emerges. We use the good German watercolors, none of those Prang 8 pan oval sets for my students.
After mine was dry, later in the day, I added some deeper watercolor hues, waited for that to dry and then added the black marker lines. the 12" x 18" size is something I never use in real life. It's for school only.