We looked at Monet's various waterlily pictures today. They noticed the reflections of the trees right away. I also had a picture of one waterlily close up and you could see that at that vantage the waterlilies just looked like splotches of color. We took this aspect of impressionistic painting for our next art project. I took pictures of flowers and other nature scenes and converted them to "cartoon" mode with my photo editing program and this rendered the photo to areas of various colors. This helped the kids see how an impressionistic painter can look at a natural object and convert it to splotches of color. Some chose outlines of the pictures to color in and others did theirs freehand.
Alex's Waterlily, made with outline (age 14)
Quentin's Rose, made with outline (age 4)
Sam's Grapes on Vine, freehand (age 10)
Katie's Lilly, freehand, (age 16)
More resources and ideas here.