Other fluorochromes all have a distinctive color associated with them. FITC is excited by blue light, but reflects back green so FITC images will be green. TRITC is excited by green light, but reflects back orange-red, so those images will be in the orange-red range.
Some material, especially plant material has the inherent ability to fluoresce, or react to specific wavelengths of light, without having any dyes or fluorochromes attached to the material. This is called "autofluorescence" and can interfere with using this research technique effectively. It is however, helpful for other tasks, such as using a plant sample when you are working to align the fluorescence illumination. This autofluorescence does not fade or quench as do biological samples so you are not damaging your cells while performing the alignment. It also allows practice in setting up photography without damaging the sample. And the bonus is that it results in beautiful images!