What's the best way to disinfect a trumpet after a cold?

You're concern is quite valid. I know many musicians who get over a cold and play for a day or two and magically have their cold symptoms return. The inside of your trumpet is a pool for bacteria as particles from your mouth gunk up in the lead mouth pipe. The best way to clean your trumpet is to get a cotton swab and some alcohol and wipe the cup of your mouthpiece. Then get a "christmas tree" and scrub the inside of the mouthpiece shank with warm water and liquid soap. This will get 80% of the bacteria that you will come in contact with. To get the other 20%, you would have buy a "snake" and do the same with the lead pipe: warm water and liquid soap. This should get rid of all the nasties in your horn. Remember to rinse your horn and mouthpiece with warm water to get the soap out, or else you will have residue, which is a bad thing.

Oh and important, there is a previous suggestion of using lysol wipes. I would not use any chemical agents on your trumpet. A majority of them can take the laquer off the horn which will make your horn look like a cat scratched all over it after a while; making it look dull and also promote rusting.

I think you mean "How can I disinfect a trumpet that was used by somebody with a cold?" as the statement that you made implies that the trumpet had a cold which is preposterous. Firstly, if you had somebody with a cold blowing a trumpet around the house, you should be more concerned that they have already blown germs all through your home. Secondly, unless you are in the habit of sharing one trumpet amongst all family members, since the person doing the blowing has, I assume, already recovered from their cold, they will have a natural immunity to any residual germs on the trumpet, since their immune system recently fought off that particular cold strain. Finally, if you still feel compelled to douse the trumpet with antibacteriological agents, you can use Lysol disinfecting wipes they make specific ones that are friendly to metallic surfaces. However, please be aware that ANTIBACTERIAL wipes will not kill cold VIRUSES, since colds are caused by a virus, not bacteria.

what kind of trumpet and what is the material it is made of?