Lee Poulsen's explanation was very interesting and clear -- a good example of a scientist or engineer who knows how much information a general audience is likely to want! When we look at flowers, we're seeing more than the color effects Lee discussed, because the surface of a flower petal is not as flat as a piece of paper or a monitor screen. There's a discussion of this in the forthcoming NARGS Rock Garden Quarterly in an article by Alan McMurtrie on hybridizing reticulata irises. He points out that the surface cells on the iris petals are of different 3-dimensional shapes depending on species or hybrid clone, and that the way the light "bounces" back and forth between the raised pigmented structures affects the way the human eye perceives the colors, because the light "picks up" extra color as it is refracted, if that's the right word, multiple times. Another writer commented that the light under which we view a color sample affects what we see. This is an effect well known to anyone who deals with fabrics, in particular. You have to take your fabric where you can see it in daylight in order to perceive it correctly. (Some kinds of artificial lighting mimic daylight more or less effectively.) I've also read that flower colors are affected by the angle of the sun at different latitudes, so that the same flower would appear different colors in, say, Arizona and Toronto. I think a lot of flowers in the blue-pink range look better in diffuse sunlight than in brilliant sun, while bright reds tend to look better in strong sun, but this is just a personal reaction. Jane McGary Northwestern Oregon, USA