I think that the "silversstone" bulbs are made this way.
Its an amber bulb coated or tinted with a thin coat of silver. What I did is I got some paint on a cotton ball and dubed (if thats the correctt word !) the bolb. Sinse the surface of the bulb is very smooth, the paint did not cover it compleatly but gathered in to small "bals". If you hold the bulb painted this way against a dark surface, it will apear silver, but if you hold it against the light it should be amber and transparent. I checked if it is shining dimmer after painting the first bulb by comparing to the unpainted onee. No difference. Had it for 2.5 month now, nothing happened, no cracks, still works.
17" Intra Signums
Euro Headlights/Clear Blinkers
White gouges (made my own)