I've seen it in opaque colors but as it is used for eliminating glare,
rendering more precise light distribution ,
providing better contrast and image definition ,
enhancing color rendition of merchandised products ,
shielding lamps from direct view ,and
reducing luminaire surface brightness for maximum visual comfort .
It seems like clear would run counter to those goals.
It'll be pink in no time so it doesn't matter much what color it starts out.