Bistability in wavelength is demonstrated using an acoustooptic deflector driven by an RF oscillator whose frequency is a non-linear function of optical wavelength. Multistable operation featuring distinct stable states in wavelength is also described. It is shown that the use of wavelength as the switching parameter in an acoustooptic deflector with a time-bandwidth product permits one to obtain up to steady states in the multistable regime. A number of stable states between 100 and 1000 times greater than those previously achieved using hybrid multistable devices in intensity are expected using this method. The switching time is given by the access time of the acoustooptic crystal. A possible application is discussed with a two-channel wavelength switch suitable for wavelength division multiplexing.