The characteristic features of the stimulated Raman backscattering of short modulated (multi-frequency) laser pulses in an underdense plasma are investigated. A laser pulse consisting of a given pair of spectral components with the frequency difference close to the double plasma frequency is studied in the weak mode coupling approximation. The scattering of the component with the higher frequency is shown to be a five-wave resonant process, and the conditions under which this process is totally suppressed are found. The scattering of the component with the lower frequency is an ordinary three-wave decay process without any suppression. When the difference between the frequencies of the two pump-field components is not close to 2\omega_{pe}, their scattering manifests itself as two independent three-wave processes. Numerical modeling is carried out to study the characteristic features of the stimulated Raman backscattering of a multifrequency (three-component) laser pulse in the regime of strong mode coupling, in which the Raman spectrum is shown to be weakly dependent on both the number of spectral components of the pump pulse and the frequency differences between them.