For those of you that are just dyeing to know :), No, it is not possible to use food colouring to dye Fabric Dryer sheets. For some reason the colour will just not stay, even with a good amount of citric acid.
So, next try. I know that tea bag dyeing works really well but those vibrant colours would be so much more fun!
I'm finally getting some time in my studio. Hopefully soon I'll have pictures of work.