To try to correlate the different observations, you'll have to understand the chemical structures. You can start by looking them up, from the box label and then online. This is likely going to be some tough chemistry, however. Some other things to try: Did you use the same amount of dye? I don't mean drops of food coloring, they may be formulated with different amounts of dyes for each color. Also, did you leave them for a long period of time? Some dyes might be slower to react.