What colour is an Airbender? If this question is not at the top of your mind, it's because you haven't been following the controversy surrounding the casting of the film The Last Airbender, set to premiere in early July. The question of ethnicity in the film's casting casts a valuable light on many of Hollywood's decisions when it comes to race and gender – and the attitudes and assumptions that underlie them.

People who make their living producing images, such as photographers, stylists, publicists, directors and pop idols, learn how to use those signs to convey the impression they want to make. Although teen girls who are trying to send a signal to their circle of friends and pop music producers who are trying to send a signal to an audience of millions are working on different scales, the principle is very much the same. Depending on your audience, you need to tailor the signals you send out very carefully. Even your age can have a certain amount of wiggle room when dressed in the right signs.