The themes we identify in this text will depend, to some extent, on how literally we understand the story (as compared to how metaphorically we might read it). Taking the story as an allegory, the theme seems to be one of social deviance. However, if we look at the story on a literal level, the themes would seem to relate more to ideas of trust and the folly of innocence in certain situations.
Seen as an allegory, the wolf represents a socially deviant impulse. Spying the child in the forest, the wold "had a very great mind to eat her up, but he dared not, because of some woodcutters working nearby in the forest." There is an indication here, in Charles Perrault's version of the tale, that the wolf's cunning is coupled with a full awareness of the nature of his actions. He wants to do something that society does not approve of.
On a literal level, the tale suggests that innocence does not always function as a shield and those who are naive may be subjected to the will of those who prey upon the trusting nature of others.
In both cases, the story deals with ideas of deception and purposeful guile. The generosity of the girl, who is going to visit her sick grandmother to deliver some food and comfort, is overwhelmed by the devious avarice of the wolf.
Another perspective available is one that interprets the tale as an assertion of wisdom as a recognition of the truths of nature. No matter what clothes a wolf may wear, it is still a dangerous, wild animal. Children (and adults) should understand that to survive in nature one must see things for what they are. Red Riding Hood projects her sense of innocence onto the natural world and suffers the consequences.