Fumed glass can be nearly any color of the rainbow. Both Silver and Gold are the most used metals for fuming.
The glass must be hot in order for the silver to stick to it. Preheat you piece of glass using nearly any size tube or rod, you can even fume colored glass. First, you must also have a rod of glass with a piece of silver on it. To do this you heat up the glass 5-10mm rod with a small small piece of silver cut and laying on your graphite. I prefer about a 6mm piece of clear glass. If your silver does not stick the first time heat the glass up again and press on the silver until the silver sticks to the glass. Once you have this not back to that piece of glass you want to fume, again make sure it is hot. How I prefer to fume is turn my torch down to a small neutral almost reduction flame. Then I put the silver in there and it will start to smoke, but sometimes is splattered first, I do not like this unless I am using it for a special technique. So I let it splatter than once it does that I then put my glass I want to fume into the flame and spin it. Now you can do too much here, only cover it. If you do too much you can burn it off with an oxidizing flame. Fuming is all about the application. Ones you have your glass fumed with silver you can do all sorts of things with it.
Gold takes fuming to the next level. Gold is best fumed on top of silver, I prefer just a slight silver fume under the gold. This also is what gets some super dope greens, what I just love! To get the gold to fume you need a little hotter more oxidizing flame. I use the same little flame for silver, just turn up the oxygen a little and it will get the gold hot enough to fume. Once you have the glass fumed you can sleeve it, draw clear lines or dot it up. You can also fume the outside or inside of the glass. Both give amazing and unique effects. Did you know at a microscopic level gold is red. The first nanotechnology was done by glass artists many, many moons ago.