The answer is (c): It will be green until it gets to the spectral green, then the same as the spectral color, as seen in an mpeg viedo by clicking your mouse on the photograph below.
When the color of the photon is green or blue, photons from the spectrum are able to excite the molecules of the fluorescein dye; as they decay the give off the characteristic green color of the dye. Colors with lesser photon energy, such as yellow, orange, and red, are not able to excite the fluorescein molecule beyond its green excitation level, they simply reflect from the fluorescent screen, although with a somewhat diminished intensity, as seen in the video.
