  We theoretically study the resonance fluorescence spectra of the lambda
($\Lambda$), vee ($V$) and cascade ($\Xi$) type three-level configurations. It
is shown that each system with two detuning frequencies can be modelled using
the $SU(3)$ symmetry group to derive a generalized optical Bloch equation. For
each configuration, this equation is solved to calculate the two-time
correlation function by invoking the quantum regression theorem. The incoherent
part of the power spectra gives the characteristic multi-peak fluorescence
profiles which are different for different configurations. We also discuss how
the dressed-state structure of such system can explain the origin of quintuplet
profile of the fluorescent spectrum.
