I'm wondering because when you light tires on fire, the smoke is black.
UPDATE: According to our esteemed Drs. Science in the comments, the burnout tire smoke is not actually smoke. It's a vapor. Sortof a tire steam, if you will. It's not a full combustion such as the tire fire above, but a superheating of the rubber. So it vaporizes.
Now we know. And knowing is half the battle. And battling is half the fun. Now I'm off to tell Matt Farah to change the title of his blog.