Hopefully, after a couple of hours, you will see some of the colour from the water on the petals. Before you read on, stop and ask yourself this question:
How has the colour got from the water to the petal?
In humans, all the nutrients and waste is transported around our bodies through blood vessels. These are little (and sometime big) pipes that connect your entire body. If you close one eye and look in a mirror you can probably see these blood vessels on your eyelid, they are little red lines.
Plants also transport waste, nutrients and water around. They do this using a special tubes. Tubes so small you can’t see them with your eye. This is why your flower has turned blue (or green, or whatever coloured food colouring you use), water has travelled up the tubes into the petals. Because the water was blue, the petals turned blue!