Try this science experiment with children over the course of several days. Fill up 4 vases with different coloured water and put 1 white carnation in each one. Watch the flowers over the next four days change to the colour of the water.
Combine milk, washing-up liquid and food colouring for this amazing effect... Add a layer of milk, then add drops of food colouring in different spots around the centre. Add one drop of washing-up liquid into the centre of the mixture OR (as in this video) prod the centre with a cotton bud with washing-up liquid on the end. [From @GE via @SarahBearchell] The science behind it is explained here: http://www.youtube.com/watch?v=hPFwDaR1g70