The present invention provides systems and methods for analyzing the excitation spectra of fluorescent particles in a flowing stream. The system uses a white light laser and color separation optics to provide a spatially-distributed, continuous color-spectrum excitation light system that is used to illuminate a region of a flowing stream. A particle that passes through the detection region traverses the full dispersed spectrum of excitation light, and the fluorescence emissions from the particle are continuously measured as it passes through the detection region. The measured fluorescence emissions at each wavelength of excitation light, which changes through full spectrum of the excitation light as the particle passes through the detection region, provides the excitation spectrum of the particle.