A confocal fluorescence microscopy setup was used to observe, in situ, spectral changes in phosphate glasses which were modified using 0.3 muJ of tightly focused 800 nm, 130 fs laser pulses. On 488 mn excitation, the modified glass shows a broad fluorescence centered at roughly 600 mn, which decays with prolonged exposure to the 488 mu light. The decay behavior is dependent on the 488 nm power, with a faster decay rate for higher powers. A mechanism whereby color centers, formed by the femtosecond pulses, fluoresce when excited by the 488 nm light and are simultaneously photobleached is proposed to explain the observed behavior.