Three-dimensional fluorescence spectra were collected from both natural-color and treated diamonds with common color centers (including N3, H3, H4, 480 nm, and N-V) to characterize the fluorescence produced by each defect. Unlike individual spectra, 3D presentations of multiple spectra allow quick and simultaneous determination of the fluorescence-producing defect(s), the excitation energy that yields maximum fluorescence intensity, the variation of fluorescence with excitation, and the peak position and band shape of individual and overall fluorescence emissions. The combination of 3D fluorescence spectra from common defects and emission spectra from several standard ultraviolet light sources revealed noticeable inconsistencies in the fluorescence observed. Our data indicate that variations in UV lamp output can significantly affect the fluorescence color observed in gem diamonds.