Only the water content (from the food colouring also) would evaporate as steam, therefore you would be left with a pink / red powdery deposit once the water has evaporated.
Hmm. Are you sure about that andymp? Try considering that food colouring goes into solution when added to water.
Don't make the mistake that this is the same sort of phenomenon that occurs when common table salt is added to water.
Today's homework. Try finding out what occurs when a colourant that is not a salt is evaporated in water. They do exist, believe it or not. Pink food colouring consists of primarily cochineal combined with other agents.
The reality is that a very dilute solution of pink food colourant will boil away within the steam but not at a discernable or visible level. Consequently, no pink/red powdery deposit will be left behind once the water has evaporated.
The steam would not be discernable pink due to the concentration involved.
If the food colouring was a liquid, rather than a dissolved solid, then it would evaporate into a vapour when it reached its boiling point. Say its boiling point was 70 degrees C. As the mixture warmed up, when the temp reached 70 degrees, the food colouring would vaporise and the temp would stay at 70 until most of it had boiled off. The temp would then rise to 100 degrees and the water would boil off. This is called fractional distillation.