NavList:

One time during the delivery of a new boat we were all  bothered by a too bright white compass light and painted the bulb red with nail polish. Would this work on the III-B?  Hewitt

I think it’s all to do with wavelengths.  A filament bulb gives out a whole spectrum of wavelengths, so there’re always a few that’ll get though nail varnish, gelatine, celluloid or whatever.  A led might emit over a much narrower band, that's one of the reasons they're so economical, so you would need to experiment, or buy the correct colour to begin with.  Having said that, I recently renewed TIKI’s masthead tri-light.  Reluctant to chuck the old one away, I thought it might make a nice decorative light at home.  I experimented by replacing the filament bulb with a cheap Far-Eastern ‘yellow square’ led array, which arrived from eBay without a specification sheet, and it worked quite giving red, white, and green sectors.  DaveP