Those of you who grow flowers can try this experiment. While researching magnesium fertilizers, I found a paper that stated that magnesium is required by most flowers to generate color pigments (as well as chlorophyll) and that is has been well-documented that roses become more vivid in color when fed magnesium. This has been tested in many flowers, but far from all. The author suggested that gardeners try adding a tablespoon per gallon of Epsom Salts to the water that is used on half your flowers and leave the salts out of the other half to see if the color changes with the addition of magnesium. My wife tried it on her Osteospermum, and it appears to make the colors brighter and more vivid on those.