Is food colouring dangerous for children to consume?

I have been hearing food colouring is dangerous for children because in a primary school production of Bugsy Malone we’re having custard pies and I decided to make them Tiswas style and use food colouring, but will it be dangerous to get food coloruing in children’s mouths for three nights in a row (Pie in face) In the end everyone gets splurged so should I alter the flan idea or will it be OK after left for one hour.