Painting on red is a good way on controlling your values. I used to paint on white and get frustrated because I felt at a disadvantage... the white stark surface, daring me to apply paint to its pristine cover. Red is the color of fire, it is exciting even before applying paint to the canvas. I know from this photo that the trees on the left hand side are too dark because they are darker than the mid value of the red. The color of the tree on the right hand side pops out against the red. It is a bluish green which is the complement of red and the same value (or close enough) to the red value. Since I began painting on a red surface several years ago there is no going back to the white canvas, and am glad of it. Enjoy
