I have observed differences in flower color, depending on the exposure to sunlight, in a variety of plants. Most of the time if is just the intensity and depth of the color of the flower, in a variety of plants from Symphytum to Christmas cactus in the house. I have noticed some Narcissus' color ages differently in a northern vs. a southern exposure, the latter bringing out more contrast between yellows and whites (as well as the reds in poeticus types). My yard has a variety of soil types. The native soils range from a rich red to a reddish brown, quick draining loam with a deep layer of red clay, volcanic, conifer derived, and alluvial containing a LOT of round river rocks (from an ancient alluvial fan, I live in a valley). Then there's an imported gray/brown clay that the landscapers put in decades ago (WHY do landscapers always use clay?!). Lastly, we have a gravel driveway, made level over the slight slope of our property, creating what could be considered a lowland pseudo-scree. It is in this gravel "scree" that I have observed a small native annual wildflower with red leaves, though they have green leaves elsewhere. My belief is that something in the gravel has been wicked into the leaves, turning them red. I've seen this in other plants too, normally where the soil is very poor. Travis Owen Rogue River, OR amateuranthecologist.blogspot.com