These light-emitting types of dyes like rhodamine & aniline blue are used to label proteins
[DOC] [TLE] Techniques for dye injection and cell labelling - The University of ... [PAR] Both pass rapidly across the cell membrane and can be used to label cells ... 
Fluorescent labels are excited by light at one wavelength and emit light at 
another ... Dyes injected for these purposes should have the following properties: 
(a) they ... similar to fluorescein in that it is excited by blue light and produces 
green.