It depends upon the subject being painted. I always taught my students to start by painting the background first as this will alleviate many problems. I have noticed that when my students started working the foreground first they met some difficulties in really matching elements in the foreground and background. Once the elements in the foreground were painted, difficulties aroused as to pay heed to the contour lines of the different element painted. An example to illustrate the said, suppose they had to paint a red circle on a green background. They will first of all paint the positive shape of circle paying heeds to the contour outline of the circle. I said " good, and now paint the background and tell about the difficulties you encouraged". Many responses were similar and one which kept on repeating was when painting the green background they had to pay caution to the edge of the already painted circle so as to avoid overlapping of green on red. Paint background first is better.
