Food: Food is the used in this novel as a metaphor for growth. Carroll is literalizing the old notion that food helps you grow big and strong, that food is the path to adulthood. Ironically, Carroll is also pointing out that growing up is only half the way to adulthood. Alice can control her size and therefore her position as an adult with the food provided by the Caterpillar, but it isnt until the Cheshire Cat shows her the dangers of adulthood that she is able to be truly adult. Food can make you big in Wonderland (as in life) but only mercy and experience can make you wise.
Red: Red is the symbol of adulthood (literally it can be taken to refer to menstrual blood, and thus fertility and vigor). The Queen and Alice are on opposite sides of this color, Alice just growing into her adulthood, the Queen just growing past it. It is over this place, this wise middle ground, that the novel fights. Red is, hopefully, a place (or an age) of balance between rules and mercy, between young and old, between wisdom and nonsense.