One way of getting round the food colouring problem is to use a liquid foundation of the correct colour instead of the food colouring. Cornflour Water A nice Blood Red food colouring Make a paste of flour and a little water and blend it into the rest of the water. Slowly bring to a simmer and stir constantly until the mixture just begins to thicken. The exact amount you will need will depend upon the number of Scouts you have, however I rarely use more than a cupful. The mixture should be used quickly as it will thicken on standing.
Some food colourings can stain clothes or skin.
Please try it out before you use it otherwise you may end up with a huge cleaning bill, multi-coloured Scouts and a queue of irate Scout parents.